png.c 151.2 KB
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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.  Oracle designates this
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 * particular file as subject to the "Classpath" exception as provided
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 * by Oracle in the LICENSE file that accompanied this code.
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
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 */

/* png.c - location for general purpose libpng functions
 *
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file and, per its terms, should not be removed:
 *
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 * Last changed in libpng 1.6.19 [November 12, 2015]
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 * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
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 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
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 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
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 */

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#include "pngpriv.h"
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/* Generate a compiler error if there is an old png.h in the search path. */
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typedef png_libpng_version_1_6_23 Your_png_h_is_not_version_1_6_23;
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/* Tells libpng that we have already handled the first "num_bytes" bytes
 * of the PNG file signature.  If the PNG data is embedded into another
 * stream we can set num_bytes = 8 so that libpng will not attempt to read
 * or write any of the magic bytes before it starts on the IHDR.
 */

#ifdef PNG_READ_SUPPORTED
void PNGAPI
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png_set_sig_bytes(png_structrp png_ptr, int num_bytes)
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{
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   unsigned int nb = (unsigned int)num_bytes;

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   png_debug(1, "in png_set_sig_bytes");

   if (png_ptr == NULL)
      return;

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   if (num_bytes < 0)
      nb = 0;

   if (nb > 8)
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      png_error(png_ptr, "Too many bytes for PNG signature");
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   png_ptr->sig_bytes = (png_byte)nb;
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}

/* Checks whether the supplied bytes match the PNG signature.  We allow
 * checking less than the full 8-byte signature so that those apps that
 * already read the first few bytes of a file to determine the file type
 * can simply check the remaining bytes for extra assurance.  Returns
 * an integer less than, equal to, or greater than zero if sig is found,
 * respectively, to be less than, to match, or be greater than the correct
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 * PNG signature (this is the same behavior as strcmp, memcmp, etc).
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 */
int PNGAPI
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png_sig_cmp(png_const_bytep sig, png_size_t start, png_size_t num_to_check)
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{
   png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
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   if (num_to_check > 8)
      num_to_check = 8;
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   else if (num_to_check < 1)
      return (-1);

   if (start > 7)
      return (-1);

   if (start + num_to_check > 8)
      num_to_check = 8 - start;

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   return ((int)(memcmp(&sig[start], &png_signature[start], num_to_check)));
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}

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#endif /* READ */
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#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
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/* Function to allocate memory for zlib */
PNG_FUNCTION(voidpf /* PRIVATE */,
png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED)
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{
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   png_alloc_size_t num_bytes = size;
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   if (png_ptr == NULL)
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      return NULL;
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   if (items >= (~(png_alloc_size_t)0)/size)
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   {
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      png_warning (png_voidcast(png_structrp, png_ptr),
         "Potential overflow in png_zalloc()");
      return NULL;
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   }

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   num_bytes *= items;
   return png_malloc_warn(png_voidcast(png_structrp, png_ptr), num_bytes);
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}

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/* Function to free memory for zlib */
void /* PRIVATE */
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png_zfree(voidpf png_ptr, voidpf ptr)
{
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   png_free(png_voidcast(png_const_structrp,png_ptr), ptr);
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}

/* Reset the CRC variable to 32 bits of 1's.  Care must be taken
 * in case CRC is > 32 bits to leave the top bits 0.
 */
void /* PRIVATE */
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png_reset_crc(png_structrp png_ptr)
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{
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   /* The cast is safe because the crc is a 32-bit value. */
   png_ptr->crc = (png_uint_32)crc32(0, Z_NULL, 0);
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}

/* Calculate the CRC over a section of data.  We can only pass as
 * much data to this routine as the largest single buffer size.  We
 * also check that this data will actually be used before going to the
 * trouble of calculating it.
 */
void /* PRIVATE */
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png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, png_size_t length)
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{
   int need_crc = 1;

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   if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0)
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   {
      if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
          (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
         need_crc = 0;
   }
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   else /* critical */
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   {
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      if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) != 0)
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         need_crc = 0;
   }

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   /* 'uLong' is defined in zlib.h as unsigned long; this means that on some
    * systems it is a 64-bit value.  crc32, however, returns 32 bits so the
    * following cast is safe.  'uInt' may be no more than 16 bits, so it is
    * necessary to perform a loop here.
    */
   if (need_crc != 0 && length > 0)
   {
      uLong crc = png_ptr->crc; /* Should never issue a warning */

      do
      {
         uInt safe_length = (uInt)length;
#ifndef __COVERITY__
         if (safe_length == 0)
            safe_length = (uInt)-1; /* evil, but safe */
#endif

         crc = crc32(crc, ptr, safe_length);

         /* The following should never issue compiler warnings; if they do the
          * target system has characteristics that will probably violate other
          * assumptions within the libpng code.
          */
         ptr += safe_length;
         length -= safe_length;
      }
      while (length > 0);

      /* And the following is always safe because the crc is only 32 bits. */
      png_ptr->crc = (png_uint_32)crc;
   }
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}

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/* Check a user supplied version number, called from both read and write
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 * functions that create a png_struct.
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 */
int
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png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver)
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{
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     /* Libpng versions 1.0.0 and later are binary compatible if the version
      * string matches through the second '.'; we must recompile any
      * applications that use any older library version.
      */

   if (user_png_ver != NULL)
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   {
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      int i = -1;
      int found_dots = 0;
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      do
      {
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         i++;
         if (user_png_ver[i] != PNG_LIBPNG_VER_STRING[i])
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            png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
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         if (user_png_ver[i] == '.')
            found_dots++;
      } while (found_dots < 2 && user_png_ver[i] != 0 &&
            PNG_LIBPNG_VER_STRING[i] != 0);
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   }

   else
      png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;

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   if ((png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH) != 0)
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   {
#ifdef PNG_WARNINGS_SUPPORTED
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      size_t pos = 0;
      char m[128];
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      pos = png_safecat(m, (sizeof m), pos,
          "Application built with libpng-");
      pos = png_safecat(m, (sizeof m), pos, user_png_ver);
      pos = png_safecat(m, (sizeof m), pos, " but running with ");
      pos = png_safecat(m, (sizeof m), pos, PNG_LIBPNG_VER_STRING);
      PNG_UNUSED(pos)
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      png_warning(png_ptr, m);
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#endif

#ifdef PNG_ERROR_NUMBERS_SUPPORTED
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      png_ptr->flags = 0;
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#endif

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      return 0;
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   }

   /* Success return. */
   return 1;
}

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/* Generic function to create a png_struct for either read or write - this
 * contains the common initialization.
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 */
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PNG_FUNCTION(png_structp /* PRIVATE */,
png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
    png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
    png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
{
   png_struct create_struct;
#  ifdef PNG_SETJMP_SUPPORTED
      jmp_buf create_jmp_buf;
#  endif

   /* This temporary stack-allocated structure is used to provide a place to
    * build enough context to allow the user provided memory allocator (if any)
    * to be called.
    */
   memset(&create_struct, 0, (sizeof create_struct));

   /* Added at libpng-1.2.6 */
#  ifdef PNG_USER_LIMITS_SUPPORTED
      create_struct.user_width_max = PNG_USER_WIDTH_MAX;
      create_struct.user_height_max = PNG_USER_HEIGHT_MAX;

#     ifdef PNG_USER_CHUNK_CACHE_MAX
      /* Added at libpng-1.2.43 and 1.4.0 */
      create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;
#     endif

#     ifdef PNG_USER_CHUNK_MALLOC_MAX
      /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists
       * in png_struct regardless.
       */
      create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;
#     endif
#  endif

   /* The following two API calls simply set fields in png_struct, so it is safe
    * to do them now even though error handling is not yet set up.
    */
#  ifdef PNG_USER_MEM_SUPPORTED
      png_set_mem_fn(&create_struct, mem_ptr, malloc_fn, free_fn);
#  else
      PNG_UNUSED(mem_ptr)
      PNG_UNUSED(malloc_fn)
      PNG_UNUSED(free_fn)
#  endif

   /* (*error_fn) can return control to the caller after the error_ptr is set,
    * this will result in a memory leak unless the error_fn does something
    * extremely sophisticated.  The design lacks merit but is implicit in the
    * API.
    */
   png_set_error_fn(&create_struct, error_ptr, error_fn, warn_fn);

#  ifdef PNG_SETJMP_SUPPORTED
      if (!setjmp(create_jmp_buf))
#  endif
      {
#  ifdef PNG_SETJMP_SUPPORTED
         /* Temporarily fake out the longjmp information until we have
          * successfully completed this function.  This only works if we have
          * setjmp() support compiled in, but it is safe - this stuff should
          * never happen.
          */
         create_struct.jmp_buf_ptr = &create_jmp_buf;
         create_struct.jmp_buf_size = 0; /*stack allocation*/
         create_struct.longjmp_fn = longjmp;
#  endif
         /* Call the general version checker (shared with read and write code):
          */
         if (png_user_version_check(&create_struct, user_png_ver) != 0)
         {
            png_structrp png_ptr = png_voidcast(png_structrp,
               png_malloc_warn(&create_struct, (sizeof *png_ptr)));

            if (png_ptr != NULL)
            {
               /* png_ptr->zstream holds a back-pointer to the png_struct, so
                * this can only be done now:
                */
               create_struct.zstream.zalloc = png_zalloc;
               create_struct.zstream.zfree = png_zfree;
               create_struct.zstream.opaque = png_ptr;

#              ifdef PNG_SETJMP_SUPPORTED
               /* Eliminate the local error handling: */
               create_struct.jmp_buf_ptr = NULL;
               create_struct.jmp_buf_size = 0;
               create_struct.longjmp_fn = 0;
#              endif

               *png_ptr = create_struct;

               /* This is the successful return point */
               return png_ptr;
            }
         }
      }

   /* A longjmp because of a bug in the application storage allocator or a
    * simple failure to allocate the png_struct.
    */
   return NULL;
}

/* Allocate the memory for an info_struct for the application. */
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PNG_FUNCTION(png_infop,PNGAPI
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png_create_info_struct,(png_const_structrp png_ptr),PNG_ALLOCATED)
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{
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   png_inforp info_ptr;
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   png_debug(1, "in png_create_info_struct");

   if (png_ptr == NULL)
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      return NULL;

   /* Use the internal API that does not (or at least should not) error out, so
    * that this call always returns ok.  The application typically sets up the
    * error handling *after* creating the info_struct because this is the way it
    * has always been done in 'example.c'.
    */
   info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr,
      (sizeof *info_ptr)));
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   if (info_ptr != NULL)
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      memset(info_ptr, 0, (sizeof *info_ptr));
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   return info_ptr;
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}

/* This function frees the memory associated with a single info struct.
 * Normally, one would use either png_destroy_read_struct() or
 * png_destroy_write_struct() to free an info struct, but this may be
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 * useful for some applications.  From libpng 1.6.0 this function is also used
 * internally to implement the png_info release part of the 'struct' destroy
 * APIs.  This ensures that all possible approaches free the same data (all of
 * it).
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 */
void PNGAPI
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png_destroy_info_struct(png_const_structrp png_ptr, png_infopp info_ptr_ptr)
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{
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   png_inforp info_ptr = NULL;
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   png_debug(1, "in png_destroy_info_struct");

   if (png_ptr == NULL)
      return;

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   if (info_ptr_ptr != NULL)
      info_ptr = *info_ptr_ptr;

   if (info_ptr != NULL)
   {
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      /* Do this first in case of an error below; if the app implements its own
       * memory management this can lead to png_free calling png_error, which
       * will abort this routine and return control to the app error handler.
       * An infinite loop may result if it then tries to free the same info
       * ptr.
       */
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      *info_ptr_ptr = NULL;
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      png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);
      memset(info_ptr, 0, (sizeof *info_ptr));
      png_free(png_ptr, info_ptr);
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   }
}

/* Initialize the info structure.  This is now an internal function (0.89)
 * and applications using it are urged to use png_create_info_struct()
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 * instead.  Use deprecated in 1.6.0, internal use removed (used internally it
 * is just a memset).
 *
 * NOTE: it is almost inconceivable that this API is used because it bypasses
 * the user-memory mechanism and the user error handling/warning mechanisms in
 * those cases where it does anything other than a memset.
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 */
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PNG_FUNCTION(void,PNGAPI
png_info_init_3,(png_infopp ptr_ptr, png_size_t png_info_struct_size),
   PNG_DEPRECATED)
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{
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   png_inforp info_ptr = *ptr_ptr;
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   png_debug(1, "in png_info_init_3");
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   if (info_ptr == NULL)
      return;
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   if ((sizeof (png_info)) > png_info_struct_size)
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   {
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      *ptr_ptr = NULL;
      /* The following line is why this API should not be used: */
      free(info_ptr);
      info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,
         (sizeof *info_ptr)));
      if (info_ptr == NULL)
         return;
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      *ptr_ptr = info_ptr;
   }
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   /* Set everything to 0 */
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   memset(info_ptr, 0, (sizeof *info_ptr));
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}

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/* The following API is not called internally */
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void PNGAPI
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png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr,
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   int freer, png_uint_32 mask)
{
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   png_debug(1, "in png_data_freer");

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   if (png_ptr == NULL || info_ptr == NULL)
      return;
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   if (freer == PNG_DESTROY_WILL_FREE_DATA)
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      info_ptr->free_me |= mask;
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   else if (freer == PNG_USER_WILL_FREE_DATA)
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      info_ptr->free_me &= ~mask;
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   else
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      png_error(png_ptr, "Unknown freer parameter in png_data_freer");
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}

void PNGAPI
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png_free_data(png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 mask,
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   int num)
{
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   png_debug(1, "in png_free_data");

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   if (png_ptr == NULL || info_ptr == NULL)
      return;

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#ifdef PNG_TEXT_SUPPORTED
   /* Free text item num or (if num == -1) all text items */
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   if (info_ptr->text != 0 &&
       ((mask & PNG_FREE_TEXT) & info_ptr->free_me) != 0)
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   {
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      if (num != -1)
      {
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         png_free(png_ptr, info_ptr->text[num].key);
         info_ptr->text[num].key = NULL;
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      }

      else
      {
         int i;
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         for (i = 0; i < info_ptr->num_text; i++)
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            png_free(png_ptr, info_ptr->text[i].key);

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         png_free(png_ptr, info_ptr->text);
         info_ptr->text = NULL;
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         info_ptr->num_text = 0;
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      }
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   }
#endif

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#ifdef PNG_tRNS_SUPPORTED
   /* Free any tRNS entry */
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   if (((mask & PNG_FREE_TRNS) & info_ptr->free_me) != 0)
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   {
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      info_ptr->valid &= ~PNG_INFO_tRNS;
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      png_free(png_ptr, info_ptr->trans_alpha);
      info_ptr->trans_alpha = NULL;
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      info_ptr->num_trans = 0;
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   }
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#endif

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#ifdef PNG_sCAL_SUPPORTED
   /* Free any sCAL entry */
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   if (((mask & PNG_FREE_SCAL) & info_ptr->free_me) != 0)
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   {
      png_free(png_ptr, info_ptr->scal_s_width);
      png_free(png_ptr, info_ptr->scal_s_height);
      info_ptr->scal_s_width = NULL;
      info_ptr->scal_s_height = NULL;
      info_ptr->valid &= ~PNG_INFO_sCAL;
   }
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#endif

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#ifdef PNG_pCAL_SUPPORTED
   /* Free any pCAL entry */
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   if (((mask & PNG_FREE_PCAL) & info_ptr->free_me) != 0)
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   {
      png_free(png_ptr, info_ptr->pcal_purpose);
      png_free(png_ptr, info_ptr->pcal_units);
      info_ptr->pcal_purpose = NULL;
      info_ptr->pcal_units = NULL;
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      if (info_ptr->pcal_params != NULL)
         {
            int i;
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            for (i = 0; i < info_ptr->pcal_nparams; i++)
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               png_free(png_ptr, info_ptr->pcal_params[i]);
550

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            png_free(png_ptr, info_ptr->pcal_params);
            info_ptr->pcal_params = NULL;
         }
      info_ptr->valid &= ~PNG_INFO_pCAL;
   }
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#endif

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#ifdef PNG_iCCP_SUPPORTED
559 560
   /* Free any profile entry */
   if (((mask & PNG_FREE_ICCP) & info_ptr->free_me) != 0)
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   {
      png_free(png_ptr, info_ptr->iccp_name);
      png_free(png_ptr, info_ptr->iccp_profile);
      info_ptr->iccp_name = NULL;
      info_ptr->iccp_profile = NULL;
      info_ptr->valid &= ~PNG_INFO_iCCP;
   }
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#endif

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#ifdef PNG_sPLT_SUPPORTED
   /* Free a given sPLT entry, or (if num == -1) all sPLT entries */
572 573
   if (info_ptr->splt_palettes != 0 &&
       ((mask & PNG_FREE_SPLT) & info_ptr->free_me) != 0)
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   {
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      if (num != -1)
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      {
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         png_free(png_ptr, info_ptr->splt_palettes[num].name);
         png_free(png_ptr, info_ptr->splt_palettes[num].entries);
         info_ptr->splt_palettes[num].name = NULL;
         info_ptr->splt_palettes[num].entries = NULL;
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      }

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      else
      {
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         int i;
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587 588 589 590
         for (i = 0; i < info_ptr->splt_palettes_num; i++)
         {
            png_free(png_ptr, info_ptr->splt_palettes[i].name);
            png_free(png_ptr, info_ptr->splt_palettes[i].entries);
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         }
592 593 594 595

         png_free(png_ptr, info_ptr->splt_palettes);
         info_ptr->splt_palettes = NULL;
         info_ptr->splt_palettes_num = 0;
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         info_ptr->valid &= ~PNG_INFO_sPLT;
      }
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   }
#endif

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#ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
   if (info_ptr->unknown_chunks != 0 &&
       ((mask & PNG_FREE_UNKN) & info_ptr->free_me) != 0)
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   {
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      if (num != -1)
      {
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          png_free(png_ptr, info_ptr->unknown_chunks[num].data);
          info_ptr->unknown_chunks[num].data = NULL;
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      }
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      else
      {
         int i;
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         for (i = 0; i < info_ptr->unknown_chunks_num; i++)
            png_free(png_ptr, info_ptr->unknown_chunks[i].data);
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         png_free(png_ptr, info_ptr->unknown_chunks);
         info_ptr->unknown_chunks = NULL;
         info_ptr->unknown_chunks_num = 0;
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      }
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   }
#endif

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#ifdef PNG_hIST_SUPPORTED
   /* Free any hIST entry */
627
   if (((mask & PNG_FREE_HIST) & info_ptr->free_me) != 0)
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   {
      png_free(png_ptr, info_ptr->hist);
      info_ptr->hist = NULL;
      info_ptr->valid &= ~PNG_INFO_hIST;
   }
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#endif

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   /* Free any PLTE entry that was internally allocated */
636
   if (((mask & PNG_FREE_PLTE) & info_ptr->free_me) != 0)
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   {
638
      png_free(png_ptr, info_ptr->palette);
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      info_ptr->palette = NULL;
      info_ptr->valid &= ~PNG_INFO_PLTE;
      info_ptr->num_palette = 0;
   }
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#ifdef PNG_INFO_IMAGE_SUPPORTED
   /* Free any image bits attached to the info structure */
646
   if (((mask & PNG_FREE_ROWS) & info_ptr->free_me) != 0)
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   {
648
      if (info_ptr->row_pointers != 0)
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      {
650 651
         png_uint_32 row;
         for (row = 0; row < info_ptr->height; row++)
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            png_free(png_ptr, info_ptr->row_pointers[row]);
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         png_free(png_ptr, info_ptr->row_pointers);
         info_ptr->row_pointers = NULL;
      }
      info_ptr->valid &= ~PNG_INFO_IDAT;
   }
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#endif

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   if (num != -1)
      mask &= ~PNG_FREE_MUL;

   info_ptr->free_me &= ~mask;
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}
666
#endif /* READ || WRITE */
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/* This function returns a pointer to the io_ptr associated with the user
 * functions.  The application should free any memory associated with this
 * pointer before png_write_destroy() or png_read_destroy() are called.
 */
png_voidp PNGAPI
673
png_get_io_ptr(png_const_structrp png_ptr)
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{
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   if (png_ptr == NULL)
      return (NULL);

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   return (png_ptr->io_ptr);
}

#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
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#  ifdef PNG_STDIO_SUPPORTED
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/* Initialize the default input/output functions for the PNG file.  If you
 * use your own read or write routines, you can call either png_set_read_fn()
 * or png_set_write_fn() instead of png_init_io().  If you have defined
686 687
 * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a
 * function of your own because "FILE *" isn't necessarily available.
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 */
void PNGAPI
690
png_init_io(png_structrp png_ptr, png_FILE_p fp)
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{
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   png_debug(1, "in png_init_io");

   if (png_ptr == NULL)
      return;

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   png_ptr->io_ptr = (png_voidp)fp;
}
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#  endif
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#  ifdef PNG_SAVE_INT_32_SUPPORTED
/* PNG signed integers are saved in 32-bit 2's complement format.  ANSI C-90
 * defines a cast of a signed integer to an unsigned integer either to preserve
 * the value, if it is positive, or to calculate:
 *
 *     (UNSIGNED_MAX+1) + integer
 *
 * Where UNSIGNED_MAX is the appropriate maximum unsigned value, so when the
 * negative integral value is added the result will be an unsigned value
 * correspnding to the 2's complement representation.
 */
void PNGAPI
png_save_int_32(png_bytep buf, png_int_32 i)
{
   png_save_uint_32(buf, i);
}
#  endif

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#  ifdef PNG_TIME_RFC1123_SUPPORTED
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/* Convert the supplied time into an RFC 1123 string suitable for use in
 * a "Creation Time" or other text-based time string.
 */
723 724
int PNGAPI
png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime)
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{
   static PNG_CONST char short_months[12][4] =
        {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
         "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};

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   if (out == NULL)
      return 0;

   if (ptime->year > 9999 /* RFC1123 limitation */ ||
       ptime->month == 0    ||  ptime->month > 12  ||
       ptime->day   == 0    ||  ptime->day   > 31  ||
       ptime->hour  > 23    ||  ptime->minute > 59 ||
       ptime->second > 60)
      return 0;
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   {
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      size_t pos = 0;
742
      char number_buf[5]; /* enough for a four-digit year */
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744
#     define APPEND_STRING(string) pos = png_safecat(out, 29, pos, (string))
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#     define APPEND_NUMBER(format, value)\
         APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))
747
#     define APPEND(ch) if (pos < 28) out[pos++] = (ch)
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749
      APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (unsigned)ptime->day);
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      APPEND(' ');
751
      APPEND_STRING(short_months[(ptime->month - 1)]);
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      APPEND(' ');
      APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year);
      APPEND(' ');
755
      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->hour);
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      APPEND(':');
757
      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->minute);
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      APPEND(':');
759
      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second);
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      APPEND_STRING(" +0000"); /* This reliably terminates the buffer */
761
      PNG_UNUSED (pos)
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#     undef APPEND
#     undef APPEND_NUMBER
#     undef APPEND_STRING
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   }

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   return 1;
}

#    if PNG_LIBPNG_VER < 10700
/* To do: remove the following from libpng-1.7 */
/* Original API that uses a private buffer in png_struct.
 * Deprecated because it causes png_struct to carry a spurious temporary
 * buffer (png_struct::time_buffer), better to have the caller pass this in.
 */
png_const_charp PNGAPI
png_convert_to_rfc1123(png_structrp png_ptr, png_const_timep ptime)
{
   if (png_ptr != NULL)
   {
      /* The only failure above if png_ptr != NULL is from an invalid ptime */
      if (png_convert_to_rfc1123_buffer(png_ptr->time_buffer, ptime) == 0)
         png_warning(png_ptr, "Ignoring invalid time value");

      else
         return png_ptr->time_buffer;
   }

   return NULL;
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}
792 793
#    endif /* LIBPNG_VER < 10700 */
#  endif /* TIME_RFC1123 */
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795
#endif /* READ || WRITE */
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png_const_charp PNGAPI
798
png_get_copyright(png_const_structrp png_ptr)
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{
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   PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */
#ifdef PNG_STRING_COPYRIGHT
   return PNG_STRING_COPYRIGHT
#else
#  ifdef __STDC__
   return PNG_STRING_NEWLINE \
806 807 808
      "libpng version 1.6.23 - June 9, 2016" PNG_STRING_NEWLINE \
      "Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson" \
      PNG_STRING_NEWLINE \
809 810 811
      "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
      "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
      PNG_STRING_NEWLINE;
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#  else
813 814
   return "libpng version 1.6.23 - June 9, 2016\
      Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson\
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      Copyright (c) 1996-1997 Andreas Dilger\
      Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
#  endif
#endif
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}

/* The following return the library version as a short string in the
 * format 1.0.0 through 99.99.99zz.  To get the version of *.h files
 * used with your application, print out PNG_LIBPNG_VER_STRING, which
 * is defined in png.h.
 * Note: now there is no difference between png_get_libpng_ver() and
 * png_get_header_ver().  Due to the version_nn_nn_nn typedef guard,
 * it is guaranteed that png.c uses the correct version of png.h.
 */
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png_const_charp PNGAPI
830
png_get_libpng_ver(png_const_structrp png_ptr)
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{
   /* Version of *.c files used when building libpng */
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   return png_get_header_ver(png_ptr);
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}

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png_const_charp PNGAPI
837
png_get_header_ver(png_const_structrp png_ptr)
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{
   /* Version of *.h files used when building libpng */
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   PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */
   return PNG_LIBPNG_VER_STRING;
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}

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png_const_charp PNGAPI
845
png_get_header_version(png_const_structrp png_ptr)
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{
   /* Returns longer string containing both version and date */
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   PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */
#ifdef __STDC__
   return PNG_HEADER_VERSION_STRING
#  ifndef PNG_READ_SUPPORTED
852
      " (NO READ SUPPORT)"
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#  endif
854
      PNG_STRING_NEWLINE;
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#else
   return PNG_HEADER_VERSION_STRING;
#endif
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}

860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917
#ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
/* NOTE: this routine is not used internally! */
/* Build a grayscale palette.  Palette is assumed to be 1 << bit_depth
 * large of png_color.  This lets grayscale images be treated as
 * paletted.  Most useful for gamma correction and simplification
 * of code.  This API is not used internally.
 */
void PNGAPI
png_build_grayscale_palette(int bit_depth, png_colorp palette)
{
   int num_palette;
   int color_inc;
   int i;
   int v;

   png_debug(1, "in png_do_build_grayscale_palette");

   if (palette == NULL)
      return;

   switch (bit_depth)
   {
      case 1:
         num_palette = 2;
         color_inc = 0xff;
         break;

      case 2:
         num_palette = 4;
         color_inc = 0x55;
         break;

      case 4:
         num_palette = 16;
         color_inc = 0x11;
         break;

      case 8:
         num_palette = 256;
         color_inc = 1;
         break;

      default:
         num_palette = 0;
         color_inc = 0;
         break;
   }

   for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
   {
      palette[i].red = (png_byte)(v & 0xff);
      palette[i].green = (png_byte)(v & 0xff);
      palette[i].blue = (png_byte)(v & 0xff);
   }
}
#endif

#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
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int PNGAPI
919
png_handle_as_unknown(png_const_structrp png_ptr, png_const_bytep chunk_name)
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{
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   /* Check chunk_name and return "keep" value if it's on the list, else 0 */
922
   png_const_bytep p, p_end;
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924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948
   if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list == 0)
      return PNG_HANDLE_CHUNK_AS_DEFAULT;

   p_end = png_ptr->chunk_list;
   p = p_end + png_ptr->num_chunk_list*5; /* beyond end */

   /* The code is the fifth byte after each four byte string.  Historically this
    * code was always searched from the end of the list, this is no longer
    * necessary because the 'set' routine handles duplicate entries correcty.
    */
   do /* num_chunk_list > 0, so at least one */
   {
      p -= 5;

      if (memcmp(chunk_name, p, 4) == 0)
         return p[4];
   }
   while (p > p_end);

   /* This means that known chunks should be processed and unknown chunks should
    * be handled according to the value of png_ptr->unknown_default; this can be
    * confusing because, as a result, there are two levels of defaulting for
    * unknown chunks.
    */
   return PNG_HANDLE_CHUNK_AS_DEFAULT;
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}
950 951 952 953 954 955 956 957 958 959 960 961 962

#if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\
   defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
int /* PRIVATE */
png_chunk_unknown_handling(png_const_structrp png_ptr, png_uint_32 chunk_name)
{
   png_byte chunk_string[5];

   PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name);
   return png_handle_as_unknown(png_ptr, chunk_string);
}
#endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */
#endif /* SET_UNKNOWN_CHUNKS */
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#ifdef PNG_READ_SUPPORTED
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/* This function, added to libpng-1.0.6g, is untested. */
int PNGAPI
967
png_reset_zstream(png_structrp png_ptr)
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{
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   if (png_ptr == NULL)
      return Z_STREAM_ERROR;

972
   /* WARNING: this resets the window bits to the maximum! */
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   return (inflateReset(&png_ptr->zstream));
}
975
#endif /* READ */
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/* This function was added to libpng-1.0.7 */
png_uint_32 PNGAPI
png_access_version_number(void)
{
   /* Version of *.c files used when building libpng */
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   return((png_uint_32)PNG_LIBPNG_VER);
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}

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#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
986 987 988 989 990 991
/* Ensure that png_ptr->zstream.msg holds some appropriate error message string.
 * If it doesn't 'ret' is used to set it to something appropriate, even in cases
 * like Z_OK or Z_STREAM_END where the error code is apparently a success code.
 */
void /* PRIVATE */
png_zstream_error(png_structrp png_ptr, int ret)
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{
993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014
   /* Translate 'ret' into an appropriate error string, priority is given to the
    * one in zstream if set.  This always returns a string, even in cases like
    * Z_OK or Z_STREAM_END where the error code is a success code.
    */
   if (png_ptr->zstream.msg == NULL) switch (ret)
   {
      default:
      case Z_OK:
         png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return code");
         break;

      case Z_STREAM_END:
         /* Normal exit */
         png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected end of LZ stream");
         break;

      case Z_NEED_DICT:
         /* This means the deflate stream did not have a dictionary; this
          * indicates a bogus PNG.
          */
         png_ptr->zstream.msg = PNGZ_MSG_CAST("missing LZ dictionary");
         break;
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1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053
      case Z_ERRNO:
         /* gz APIs only: should not happen */
         png_ptr->zstream.msg = PNGZ_MSG_CAST("zlib IO error");
         break;

      case Z_STREAM_ERROR:
         /* internal libpng error */
         png_ptr->zstream.msg = PNGZ_MSG_CAST("bad parameters to zlib");
         break;

      case Z_DATA_ERROR:
         png_ptr->zstream.msg = PNGZ_MSG_CAST("damaged LZ stream");
         break;

      case Z_MEM_ERROR:
         png_ptr->zstream.msg = PNGZ_MSG_CAST("insufficient memory");
         break;

      case Z_BUF_ERROR:
         /* End of input or output; not a problem if the caller is doing
          * incremental read or write.
          */
         png_ptr->zstream.msg = PNGZ_MSG_CAST("truncated");
         break;

      case Z_VERSION_ERROR:
         png_ptr->zstream.msg = PNGZ_MSG_CAST("unsupported zlib version");
         break;

      case PNG_UNEXPECTED_ZLIB_RETURN:
         /* Compile errors here mean that zlib now uses the value co-opted in
          * pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above
          * and change pngpriv.h.  Note that this message is "... return",
          * whereas the default/Z_OK one is "... return code".
          */
         png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return");
         break;
   }
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}
1055 1056 1057 1058

/* png_convert_size: a PNGAPI but no longer in png.h, so deleted
 * at libpng 1.5.5!
 */
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/* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */
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#ifdef PNG_GAMMA_SUPPORTED /* always set if COLORSPACE */
static int
png_colorspace_check_gamma(png_const_structrp png_ptr,
   png_colorspacerp colorspace, png_fixed_point gAMA, int from)
   /* This is called to check a new gamma value against an existing one.  The
    * routine returns false if the new gamma value should not be written.
    *
    * 'from' says where the new gamma value comes from:
    *
    *    0: the new gamma value is the libpng estimate for an ICC profile
    *    1: the new gamma value comes from a gAMA chunk
    *    2: the new gamma value comes from an sRGB chunk
    */
{
   png_fixed_point gtest;

   if ((colorspace->flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&
      (png_muldiv(&gtest, colorspace->gamma, PNG_FP_1, gAMA) == 0  ||
      png_gamma_significant(gtest) != 0))
   {
      /* Either this is an sRGB image, in which case the calculated gamma
       * approximation should match, or this is an image with a profile and the
       * value libpng calculates for the gamma of the profile does not match the
       * value recorded in the file.  The former, sRGB, case is an error, the
       * latter is just a warning.
       */
      if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0 || from == 2)
      {
         png_chunk_report(png_ptr, "gamma value does not match sRGB",
            PNG_CHUNK_ERROR);
         /* Do not overwrite an sRGB value */
         return from == 2;
      }

      else /* sRGB tag not involved */
      {
         png_chunk_report(png_ptr, "gamma value does not match libpng estimate",
            PNG_CHUNK_WARNING);
         return from == 1;
      }
   }

   return 1;
}

void /* PRIVATE */
png_colorspace_set_gamma(png_const_structrp png_ptr,
   png_colorspacerp colorspace, png_fixed_point gAMA)
{
   /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't
    * occur.  Since the fixed point representation is asymetrical it is
    * possible for 1/gamma to overflow the limit of 21474 and this means the
    * gamma value must be at least 5/100000 and hence at most 20000.0.  For
    * safety the limits here are a little narrower.  The values are 0.00016 to
    * 6250.0, which are truly ridiculous gamma values (and will produce
    * displays that are all black or all white.)
    *
    * In 1.6.0 this test replaces the ones in pngrutil.c, in the gAMA chunk
    * handling code, which only required the value to be >0.
    */
   png_const_charp errmsg;

   if (gAMA < 16 || gAMA > 625000000)
      errmsg = "gamma value out of range";

#  ifdef PNG_READ_gAMA_SUPPORTED
   /* Allow the application to set the gamma value more than once */
   else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
      (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)
      errmsg = "duplicate";
#  endif

   /* Do nothing if the colorspace is already invalid */
   else if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
      return;

   else
   {
      if (png_colorspace_check_gamma(png_ptr, colorspace, gAMA,
          1/*from gAMA*/) != 0)
      {
         /* Store this gamma value. */
         colorspace->gamma = gAMA;
         colorspace->flags |=
            (PNG_COLORSPACE_HAVE_GAMMA | PNG_COLORSPACE_FROM_gAMA);
      }

      /* At present if the check_gamma test fails the gamma of the colorspace is
       * not updated however the colorspace is not invalidated.  This
       * corresponds to the case where the existing gamma comes from an sRGB
       * chunk or profile.  An error message has already been output.
       */
      return;
   }

   /* Error exit - errmsg has been set. */
   colorspace->flags |= PNG_COLORSPACE_INVALID;
   png_chunk_report(png_ptr, errmsg, PNG_CHUNK_WRITE_ERROR);
}

void /* PRIVATE */
png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr)
{
   if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
   {
      /* Everything is invalid */
      info_ptr->valid &= ~(PNG_INFO_gAMA|PNG_INFO_cHRM|PNG_INFO_sRGB|
         PNG_INFO_iCCP);

#     ifdef PNG_COLORSPACE_SUPPORTED
      /* Clean up the iCCP profile now if it won't be used. */
      png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);
#     else
      PNG_UNUSED(png_ptr)
#     endif
   }

   else
   {
#     ifdef PNG_COLORSPACE_SUPPORTED
      /* Leave the INFO_iCCP flag set if the pngset.c code has already set
       * it; this allows a PNG to contain a profile which matches sRGB and
       * yet still have that profile retrievable by the application.
       */
      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB) != 0)
         info_ptr->valid |= PNG_INFO_sRGB;

      else
         info_ptr->valid &= ~PNG_INFO_sRGB;

      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
         info_ptr->valid |= PNG_INFO_cHRM;

      else
         info_ptr->valid &= ~PNG_INFO_cHRM;
#     endif

      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0)
         info_ptr->valid |= PNG_INFO_gAMA;

      else
         info_ptr->valid &= ~PNG_INFO_gAMA;
   }
}

#ifdef PNG_READ_SUPPORTED
void /* PRIVATE */
png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr)
{
   if (info_ptr == NULL) /* reduce code size; check here not in the caller */
      return;

   info_ptr->colorspace = png_ptr->colorspace;
   png_colorspace_sync_info(png_ptr, info_ptr);
}
#endif
#endif /* GAMMA */

#ifdef PNG_COLORSPACE_SUPPORTED
/* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for
 * cHRM, as opposed to using chromaticities.  These internal APIs return
 * non-zero on a parameter error.  The X, Y and Z values are required to be
 * positive and less than 1.0.
 */
static int
png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ)
{
   png_int_32 d, dwhite, whiteX, whiteY;

   d = XYZ->red_X + XYZ->red_Y + XYZ->red_Z;
   if (png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, d) == 0)
      return 1;
   if (png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d) == 0)
      return 1;
   dwhite = d;
   whiteX = XYZ->red_X;
   whiteY = XYZ->red_Y;

   d = XYZ->green_X + XYZ->green_Y + XYZ->green_Z;
   if (png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, d) == 0)
      return 1;
   if (png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d) == 0)
      return 1;
   dwhite += d;
   whiteX += XYZ->green_X;
   whiteY += XYZ->green_Y;

   d = XYZ->blue_X + XYZ->blue_Y + XYZ->blue_Z;
   if (png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, d) == 0)
      return 1;
   if (png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d) == 0)
      return 1;
   dwhite += d;
   whiteX += XYZ->blue_X;
   whiteY += XYZ->blue_Y;

   /* The reference white is simply the sum of the end-point (X,Y,Z) vectors,
    * thus:
    */
   if (png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite) == 0)
      return 1;
   if (png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite) == 0)
      return 1;

   return 0;
}

static int
png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy)
{
   png_fixed_point red_inverse, green_inverse, blue_scale;
   png_fixed_point left, right, denominator;

   /* Check xy and, implicitly, z.  Note that wide gamut color spaces typically
    * have end points with 0 tristimulus values (these are impossible end
    * points, but they are used to cover the possible colors).  We check
    * xy->whitey against 5, not 0, to avoid a possible integer overflow.
    */
   if (xy->redx   < 0 || xy->redx > PNG_FP_1) return 1;
   if (xy->redy   < 0 || xy->redy > PNG_FP_1-xy->redx) return 1;
   if (xy->greenx < 0 || xy->greenx > PNG_FP_1) return 1;
   if (xy->greeny < 0 || xy->greeny > PNG_FP_1-xy->greenx) return 1;
   if (xy->bluex  < 0 || xy->bluex > PNG_FP_1) return 1;
   if (xy->bluey  < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1;
   if (xy->whitex < 0 || xy->whitex > PNG_FP_1) return 1;
   if (xy->whitey < 5 || xy->whitey > PNG_FP_1-xy->whitex) return 1;

   /* The reverse calculation is more difficult because the original tristimulus
    * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8
    * derived values were recorded in the cHRM chunk;
    * (red,green,blue,white)x(x,y).  This loses one degree of freedom and
    * therefore an arbitrary ninth value has to be introduced to undo the
    * original transformations.
    *
    * Think of the original end-points as points in (X,Y,Z) space.  The
    * chromaticity values (c) have the property:
    *
    *           C
    *   c = ---------
    *       X + Y + Z
    *
    * For each c (x,y,z) from the corresponding original C (X,Y,Z).  Thus the
    * three chromaticity values (x,y,z) for each end-point obey the
    * relationship:
    *
    *   x + y + z = 1
    *
    * This describes the plane in (X,Y,Z) space that intersects each axis at the
    * value 1.0; call this the chromaticity plane.  Thus the chromaticity
    * calculation has scaled each end-point so that it is on the x+y+z=1 plane
    * and chromaticity is the intersection of the vector from the origin to the
    * (X,Y,Z) value with the chromaticity plane.
    *
    * To fully invert the chromaticity calculation we would need the three
    * end-point scale factors, (red-scale, green-scale, blue-scale), but these
    * were not recorded.  Instead we calculated the reference white (X,Y,Z) and
    * recorded the chromaticity of this.  The reference white (X,Y,Z) would have
    * given all three of the scale factors since:
    *
    *    color-C = color-c * color-scale
    *    white-C = red-C + green-C + blue-C
    *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
    *
    * But cHRM records only white-x and white-y, so we have lost the white scale
    * factor:
    *
    *    white-C = white-c*white-scale
    *
    * To handle this the inverse transformation makes an arbitrary assumption
    * about white-scale:
    *
    *    Assume: white-Y = 1.0
    *    Hence:  white-scale = 1/white-y
    *    Or:     red-Y + green-Y + blue-Y = 1.0
    *
    * Notice the last statement of the assumption gives an equation in three of
    * the nine values we want to calculate.  8 more equations come from the
    * above routine as summarised at the top above (the chromaticity
    * calculation):
    *
    *    Given: color-x = color-X / (color-X + color-Y + color-Z)
    *    Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0
    *
    * This is 9 simultaneous equations in the 9 variables "color-C" and can be
    * solved by Cramer's rule.  Cramer's rule requires calculating 10 9x9 matrix
    * determinants, however this is not as bad as it seems because only 28 of
    * the total of 90 terms in the various matrices are non-zero.  Nevertheless
    * Cramer's rule is notoriously numerically unstable because the determinant
    * calculation involves the difference of large, but similar, numbers.  It is
    * difficult to be sure that the calculation is stable for real world values
    * and it is certain that it becomes unstable where the end points are close
    * together.
    *
    * So this code uses the perhaps slightly less optimal but more
    * understandable and totally obvious approach of calculating color-scale.
    *
    * This algorithm depends on the precision in white-scale and that is
    * (1/white-y), so we can immediately see that as white-y approaches 0 the
    * accuracy inherent in the cHRM chunk drops off substantially.
    *
    * libpng arithmetic: a simple inversion of the above equations
    * ------------------------------------------------------------
    *
    *    white_scale = 1/white-y
    *    white-X = white-x * white-scale
    *    white-Y = 1.0
    *    white-Z = (1 - white-x - white-y) * white_scale
    *
    *    white-C = red-C + green-C + blue-C
    *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
    *
    * This gives us three equations in (red-scale,green-scale,blue-scale) where
    * all the coefficients are now known:
    *
    *    red-x*red-scale + green-x*green-scale + blue-x*blue-scale
    *       = white-x/white-y
    *    red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1
    *    red-z*red-scale + green-z*green-scale + blue-z*blue-scale
    *       = (1 - white-x - white-y)/white-y
    *
    * In the last equation color-z is (1 - color-x - color-y) so we can add all
    * three equations together to get an alternative third:
    *
    *    red-scale + green-scale + blue-scale = 1/white-y = white-scale
    *
    * So now we have a Cramer's rule solution where the determinants are just
    * 3x3 - far more tractible.  Unfortunately 3x3 determinants still involve
    * multiplication of three coefficients so we can't guarantee to avoid
    * overflow in the libpng fixed point representation.  Using Cramer's rule in
    * floating point is probably a good choice here, but it's not an option for
    * fixed point.  Instead proceed to simplify the first two equations by
    * eliminating what is likely to be the largest value, blue-scale:
    *
    *    blue-scale = white-scale - red-scale - green-scale
    *
    * Hence:
    *
    *    (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale =
    *                (white-x - blue-x)*white-scale
    *
    *    (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale =
    *                1 - blue-y*white-scale
    *
    * And now we can trivially solve for (red-scale,green-scale):
    *
    *    green-scale =
    *                (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale
    *                -----------------------------------------------------------
    *                                  green-x - blue-x
    *
    *    red-scale =
    *                1 - blue-y*white-scale - (green-y - blue-y) * green-scale
    *                ---------------------------------------------------------
    *                                  red-y - blue-y
    *
    * Hence:
    *
    *    red-scale =
    *          ( (green-x - blue-x) * (white-y - blue-y) -
    *            (green-y - blue-y) * (white-x - blue-x) ) / white-y
    * -------------------------------------------------------------------------
    *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
    *
    *    green-scale =
    *          ( (red-y - blue-y) * (white-x - blue-x) -
    *            (red-x - blue-x) * (white-y - blue-y) ) / white-y
    * -------------------------------------------------------------------------
    *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
    *
    * Accuracy:
    * The input values have 5 decimal digits of accuracy.  The values are all in
    * the range 0 < value < 1, so simple products are in the same range but may
    * need up to 10 decimal digits to preserve the original precision and avoid
    * underflow.  Because we are using a 32-bit signed representation we cannot
    * match this; the best is a little over 9 decimal digits, less than 10.
    *
    * The approach used here is to preserve the maximum precision within the
    * signed representation.  Because the red-scale calculation above uses the
    * difference between two products of values that must be in the range -1..+1
    * it is sufficient to divide the product by 7; ceil(100,000/32767*2).  The
    * factor is irrelevant in the calculation because it is applied to both
    * numerator and denominator.
    *
    * Note that the values of the differences of the products of the
    * chromaticities in the above equations tend to be small, for example for
    * the sRGB chromaticities they are:
    *
    * red numerator:    -0.04751
    * green numerator:  -0.08788
    * denominator:      -0.2241 (without white-y multiplication)
    *
    *  The resultant Y coefficients from the chromaticities of some widely used
    *  color space definitions are (to 15 decimal places):
    *
    *  sRGB
    *    0.212639005871510 0.715168678767756 0.072192315360734
    *  Kodak ProPhoto
    *    0.288071128229293 0.711843217810102 0.000085653960605
    *  Adobe RGB
    *    0.297344975250536 0.627363566255466 0.075291458493998
    *  Adobe Wide Gamut RGB
    *    0.258728243040113 0.724682314948566 0.016589442011321
    */
   /* By the argument, above overflow should be impossible here. The return
    * value of 2 indicates an internal error to the caller.
    */
   if (png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 7) == 0)
      return 2;
   if (png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 7) == 0)
      return 2;
   denominator = left - right;

   /* Now find the red numerator. */
   if (png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 7) == 0)
      return 2;
   if (png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 7) == 0)
      return 2;

   /* Overflow is possible here and it indicates an extreme set of PNG cHRM
    * chunk values.  This calculation actually returns the reciprocal of the
    * scale value because this allows us to delay the multiplication of white-y
    * into the denominator, which tends to produce a small number.
    */
   if (png_muldiv(&red_inverse, xy->whitey, denominator, left-right) == 0 ||
       red_inverse <= xy->whitey /* r+g+b scales = white scale */)
      return 1;

   /* Similarly for green_inverse: */
   if (png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 7) == 0)
      return 2;
   if (png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 7) == 0)
      return 2;
   if (png_muldiv(&green_inverse, xy->whitey, denominator, left-right) == 0 ||
       green_inverse <= xy->whitey)
      return 1;

   /* And the blue scale, the checks above guarantee this can't overflow but it
    * can still produce 0 for extreme cHRM values.
    */
   blue_scale = png_reciprocal(xy->whitey) - png_reciprocal(red_inverse) -
       png_reciprocal(green_inverse);
   if (blue_scale <= 0)
      return 1;


   /* And fill in the png_XYZ: */
   if (png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse) == 0)
      return 1;
   if (png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse) == 0)
      return 1;
   if (png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1,
       red_inverse) == 0)
      return 1;

   if (png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse) == 0)
      return 1;
   if (png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse) == 0)
      return 1;
   if (png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1,
       green_inverse) == 0)
      return 1;

   if (png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1) == 0)
      return 1;
   if (png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1) == 0)
      return 1;
   if (png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,
       PNG_FP_1) == 0)
      return 1;

   return 0; /*success*/
}

static int
png_XYZ_normalize(png_XYZ *XYZ)
{
   png_int_32 Y;

   if (XYZ->red_Y < 0 || XYZ->green_Y < 0 || XYZ->blue_Y < 0 ||
      XYZ->red_X < 0 || XYZ->green_X < 0 || XYZ->blue_X < 0 ||
      XYZ->red_Z < 0 || XYZ->green_Z < 0 || XYZ->blue_Z < 0)
      return 1;

   /* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1.
    * IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore
    * relying on addition of two positive values producing a negative one is not
    * safe.
    */
   Y = XYZ->red_Y;
   if (0x7fffffff - Y < XYZ->green_X)
      return 1;
   Y += XYZ->green_Y;
   if (0x7fffffff - Y < XYZ->blue_X)
      return 1;
   Y += XYZ->blue_Y;

   if (Y != PNG_FP_1)
   {
      if (png_muldiv(&XYZ->red_X, XYZ->red_X, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y) == 0)
         return 1;

      if (png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y) == 0)
         return 1;

      if (png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y) == 0)
         return 1;
      if (png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y) == 0)
         return 1;
   }

   return 0;
}

static int
png_colorspace_endpoints_match(const png_xy *xy1, const png_xy *xy2, int delta)
{
   /* Allow an error of +/-0.01 (absolute value) on each chromaticity */
   if (PNG_OUT_OF_RANGE(xy1->whitex, xy2->whitex,delta) ||
       PNG_OUT_OF_RANGE(xy1->whitey, xy2->whitey,delta) ||
       PNG_OUT_OF_RANGE(xy1->redx,   xy2->redx,  delta) ||
       PNG_OUT_OF_RANGE(xy1->redy,   xy2->redy,  delta) ||
       PNG_OUT_OF_RANGE(xy1->greenx, xy2->greenx,delta) ||
       PNG_OUT_OF_RANGE(xy1->greeny, xy2->greeny,delta) ||
       PNG_OUT_OF_RANGE(xy1->bluex,  xy2->bluex, delta) ||
       PNG_OUT_OF_RANGE(xy1->bluey,  xy2->bluey, delta))
      return 0;
   return 1;
}

/* Added in libpng-1.6.0, a different check for the validity of a set of cHRM
 * chunk chromaticities.  Earlier checks used to simply look for the overflow
 * condition (where the determinant of the matrix to solve for XYZ ends up zero
 * because the chromaticity values are not all distinct.)  Despite this it is
 * theoretically possible to produce chromaticities that are apparently valid
 * but that rapidly degrade to invalid, potentially crashing, sets because of
 * arithmetic inaccuracies when calculations are performed on them.  The new
 * check is to round-trip xy -> XYZ -> xy and then check that the result is
 * within a small percentage of the original.
 */
static int
png_colorspace_check_xy(png_XYZ *XYZ, const png_xy *xy)
{
   int result;
   png_xy xy_test;

   /* As a side-effect this routine also returns the XYZ endpoints. */
   result = png_XYZ_from_xy(XYZ, xy);
   if (result != 0)
      return result;

   result = png_xy_from_XYZ(&xy_test, XYZ);
   if (result != 0)
      return result;

   if (png_colorspace_endpoints_match(xy, &xy_test,
       5/*actually, the math is pretty accurate*/) != 0)
      return 0;

   /* Too much slip */
   return 1;
}

/* This is the check going the other way.  The XYZ is modified to normalize it
 * (another side-effect) and the xy chromaticities are returned.
 */
static int
png_colorspace_check_XYZ(png_xy *xy, png_XYZ *XYZ)
{
   int result;
   png_XYZ XYZtemp;

   result = png_XYZ_normalize(XYZ);
   if (result != 0)
      return result;

   result = png_xy_from_XYZ(xy, XYZ);
   if (result != 0)
      return result;

   XYZtemp = *XYZ;
   return png_colorspace_check_xy(&XYZtemp, xy);
}

/* Used to check for an endpoint match against sRGB */
static const png_xy sRGB_xy = /* From ITU-R BT.709-3 */
{
   /* color      x       y */
   /* red   */ 64000, 33000,
   /* green */ 30000, 60000,
   /* blue  */ 15000,  6000,
   /* white */ 31270, 32900
};

static int
png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr,
   png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ,
   int preferred)
{
   if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
      return 0;

   /* The consistency check is performed on the chromaticities; this factors out
    * variations because of the normalization (or not) of the end point Y
    * values.
    */
   if (preferred < 2 &&
       (colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
   {
      /* The end points must be reasonably close to any we already have.  The
       * following allows an error of up to +/-.001
       */
      if (png_colorspace_endpoints_match(xy, &colorspace->end_points_xy,
          100) == 0)
      {
         colorspace->flags |= PNG_COLORSPACE_INVALID;
         png_benign_error(png_ptr, "inconsistent chromaticities");
         return 0; /* failed */
      }

      /* Only overwrite with preferred values */
      if (preferred == 0)
         return 1; /* ok, but no change */
   }

   colorspace->end_points_xy = *xy;
   colorspace->end_points_XYZ = *XYZ;
   colorspace->flags |= PNG_COLORSPACE_HAVE_ENDPOINTS;

   /* The end points are normally quoted to two decimal digits, so allow +/-0.01
    * on this test.
    */
   if (png_colorspace_endpoints_match(xy, &sRGB_xy, 1000) != 0)
      colorspace->flags |= PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB;

   else
      colorspace->flags &= PNG_COLORSPACE_CANCEL(
         PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);

   return 2; /* ok and changed */
}

int /* PRIVATE */
png_colorspace_set_chromaticities(png_const_structrp png_ptr,
   png_colorspacerp colorspace, const png_xy *xy, int preferred)
{
   /* We must check the end points to ensure they are reasonable - in the past
    * color management systems have crashed as a result of getting bogus
    * colorant values, while this isn't the fault of libpng it is the
    * responsibility of libpng because PNG carries the bomb and libpng is in a
    * position to protect against it.
    */
   png_XYZ XYZ;

   switch (png_colorspace_check_xy(&XYZ, xy))
   {
      case 0: /* success */
         return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, xy, &XYZ,
            preferred);

      case 1:
         /* We can't invert the chromaticities so we can't produce value XYZ
          * values.  Likely as not a color management system will fail too.
          */
         colorspace->flags |= PNG_COLORSPACE_INVALID;
         png_benign_error(png_ptr, "invalid chromaticities");
         break;

      default:
         /* libpng is broken; this should be a warning but if it happens we
          * want error reports so for the moment it is an error.
          */
         colorspace->flags |= PNG_COLORSPACE_INVALID;
         png_error(png_ptr, "internal error checking chromaticities");
   }

   return 0; /* failed */
}

int /* PRIVATE */
png_colorspace_set_endpoints(png_const_structrp png_ptr,
   png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred)
{
   png_XYZ XYZ = *XYZ_in;
   png_xy xy;

   switch (png_colorspace_check_XYZ(&xy, &XYZ))
   {
      case 0:
         return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, &xy, &XYZ,
            preferred);

      case 1:
         /* End points are invalid. */
         colorspace->flags |= PNG_COLORSPACE_INVALID;
         png_benign_error(png_ptr, "invalid end points");
         break;

      default:
         colorspace->flags |= PNG_COLORSPACE_INVALID;
         png_error(png_ptr, "internal error checking chromaticities");
   }

   return 0; /* failed */
}

#if defined(PNG_sRGB_SUPPORTED) || defined(PNG_iCCP_SUPPORTED)
/* Error message generation */
static char
png_icc_tag_char(png_uint_32 byte)
{
   byte &= 0xff;
   if (byte >= 32 && byte <= 126)
      return (char)byte;
   else
      return '?';
}

static void
png_icc_tag_name(char *name, png_uint_32 tag)
{
   name[0] = '\'';
   name[1] = png_icc_tag_char(tag >> 24);
   name[2] = png_icc_tag_char(tag >> 16);
   name[3] = png_icc_tag_char(tag >>  8);
   name[4] = png_icc_tag_char(tag      );
   name[5] = '\'';
}

static int
is_ICC_signature_char(png_alloc_size_t it)
{
   return it == 32 || (it >= 48 && it <= 57) || (it >= 65 && it <= 90) ||
      (it >= 97 && it <= 122);
}

static int
is_ICC_signature(png_alloc_size_t it)
{
   return is_ICC_signature_char(it >> 24) /* checks all the top bits */ &&
      is_ICC_signature_char((it >> 16) & 0xff) &&
      is_ICC_signature_char((it >> 8) & 0xff) &&
      is_ICC_signature_char(it & 0xff);
}

static int
png_icc_profile_error(png_const_structrp png_ptr, png_colorspacerp colorspace,
   png_const_charp name, png_alloc_size_t value, png_const_charp reason)
{
   size_t pos;
   char message[196]; /* see below for calculation */

   if (colorspace != NULL)
      colorspace->flags |= PNG_COLORSPACE_INVALID;

   pos = png_safecat(message, (sizeof message), 0, "profile '"); /* 9 chars */
   pos = png_safecat(message, pos+79, pos, name); /* Truncate to 79 chars */
   pos = png_safecat(message, (sizeof message), pos, "': "); /* +2 = 90 */
   if (is_ICC_signature(value) != 0)
   {
      /* So 'value' is at most 4 bytes and the following cast is safe */
      png_icc_tag_name(message+pos, (png_uint_32)value);
      pos += 6; /* total +8; less than the else clause */
      message[pos++] = ':';
      message[pos++] = ' ';
   }
#  ifdef PNG_WARNINGS_SUPPORTED
   else
      {
         char number[PNG_NUMBER_BUFFER_SIZE]; /* +24 = 114*/

         pos = png_safecat(message, (sizeof message), pos,
            png_format_number(number, number+(sizeof number),
               PNG_NUMBER_FORMAT_x, value));
         pos = png_safecat(message, (sizeof message), pos, "h: "); /*+2 = 116*/
      }
#  endif
   /* The 'reason' is an arbitrary message, allow +79 maximum 195 */
   pos = png_safecat(message, (sizeof message), pos, reason);
   PNG_UNUSED(pos)

   /* This is recoverable, but make it unconditionally an app_error on write to
    * avoid writing invalid ICC profiles into PNG files (i.e., we handle them
    * on read, with a warning, but on write unless the app turns off
    * application errors the PNG won't be written.)
    */
   png_chunk_report(png_ptr, message,
      (colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR);

   return 0;
}
#endif /* sRGB || iCCP */

#ifdef PNG_sRGB_SUPPORTED
int /* PRIVATE */
png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace,
   int intent)
{
   /* sRGB sets known gamma, end points and (from the chunk) intent. */
   /* IMPORTANT: these are not necessarily the values found in an ICC profile
    * because ICC profiles store values adapted to a D50 environment; it is
    * expected that the ICC profile mediaWhitePointTag will be D50; see the
    * checks and code elsewhere to understand this better.
    *
    * These XYZ values, which are accurate to 5dp, produce rgb to gray
    * coefficients of (6968,23435,2366), which are reduced (because they add up
    * to 32769 not 32768) to (6968,23434,2366).  These are the values that
    * libpng has traditionally used (and are the best values given the 15bit
    * algorithm used by the rgb to gray code.)
    */
   static const png_XYZ sRGB_XYZ = /* D65 XYZ (*not* the D50 adapted values!) */
   {
      /* color      X      Y      Z */
      /* red   */ 41239, 21264,  1933,
      /* green */ 35758, 71517, 11919,
      /* blue  */ 18048,  7219, 95053
   };

   /* Do nothing if the colorspace is already invalidated. */
   if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
      return 0;

   /* Check the intent, then check for existing settings.  It is valid for the
    * PNG file to have cHRM or gAMA chunks along with sRGB, but the values must
    * be consistent with the correct values.  If, however, this function is
    * called below because an iCCP chunk matches sRGB then it is quite
    * conceivable that an older app recorded incorrect gAMA and cHRM because of
    * an incorrect calculation based on the values in the profile - this does
    * *not* invalidate the profile (though it still produces an error, which can
    * be ignored.)
    */
   if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST)
      return png_icc_profile_error(png_ptr, colorspace, "sRGB",
         (unsigned)intent, "invalid sRGB rendering intent");

   if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 &&
      colorspace->rendering_intent != intent)
      return png_icc_profile_error(png_ptr, colorspace, "sRGB",
         (unsigned)intent, "inconsistent rendering intents");

   if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0)
   {
      png_benign_error(png_ptr, "duplicate sRGB information ignored");
      return 0;
   }

   /* If the standard sRGB cHRM chunk does not match the one from the PNG file
    * warn but overwrite the value with the correct one.
    */
   if ((colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0 &&
      !png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy,
         100))
      png_chunk_report(png_ptr, "cHRM chunk does not match sRGB",
         PNG_CHUNK_ERROR);

   /* This check is just done for the error reporting - the routine always
    * returns true when the 'from' argument corresponds to sRGB (2).
    */
   (void)png_colorspace_check_gamma(png_ptr, colorspace, PNG_GAMMA_sRGB_INVERSE,
      2/*from sRGB*/);

   /* intent: bugs in GCC force 'int' to be used as the parameter type. */
   colorspace->rendering_intent = (png_uint_16)intent;
   colorspace->flags |= PNG_COLORSPACE_HAVE_INTENT;

   /* endpoints */
   colorspace->end_points_xy = sRGB_xy;
   colorspace->end_points_XYZ = sRGB_XYZ;
   colorspace->flags |=
      (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);

   /* gamma */
   colorspace->gamma = PNG_GAMMA_sRGB_INVERSE;
   colorspace->flags |= PNG_COLORSPACE_HAVE_GAMMA;

   /* Finally record that we have an sRGB profile */
   colorspace->flags |=
      (PNG_COLORSPACE_MATCHES_sRGB|PNG_COLORSPACE_FROM_sRGB);

   return 1; /* set */
}
#endif /* sRGB */

#ifdef PNG_iCCP_SUPPORTED
/* Encoded value of D50 as an ICC XYZNumber.  From the ICC 2010 spec the value
 * is XYZ(0.9642,1.0,0.8249), which scales to:
 *
 *    (63189.8112, 65536, 54060.6464)
 */
static const png_byte D50_nCIEXYZ[12] =
   { 0x00, 0x00, 0xf6, 0xd6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d };

int /* PRIVATE */
png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace,
   png_const_charp name, png_uint_32 profile_length)
{
   if (profile_length < 132)
      return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
         "too short");

   return 1;
}

int /* PRIVATE */
png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,
   png_const_charp name, png_uint_32 profile_length,
   png_const_bytep profile/* first 132 bytes only */, int color_type)
{
   png_uint_32 temp;

   /* Length check; this cannot be ignored in this code because profile_length
    * is used later to check the tag table, so even if the profile seems over
    * long profile_length from the caller must be correct.  The caller can fix
    * this up on read or write by just passing in the profile header length.
    */
   temp = png_get_uint_32(profile);
   if (temp != profile_length)
      return png_icc_profile_error(png_ptr, colorspace, name, temp,
         "length does not match profile");

   temp = (png_uint_32) (*(profile+8));
   if (temp > 3 && (profile_length & 3))
      return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
         "invalid length");

   temp = png_get_uint_32(profile+128); /* tag count: 12 bytes/tag */
   if (temp > 357913930 || /* (2^32-4-132)/12: maximum possible tag count */
      profile_length < 132+12*temp) /* truncated tag table */
      return png_icc_profile_error(png_ptr, colorspace, name, temp,
         "tag count too large");

   /* The 'intent' must be valid or we can't store it, ICC limits the intent to
    * 16 bits.
    */
   temp = png_get_uint_32(profile+64);
   if (temp >= 0xffff) /* The ICC limit */
      return png_icc_profile_error(png_ptr, colorspace, name, temp,
         "invalid rendering intent");

   /* This is just a warning because the profile may be valid in future
    * versions.
    */
   if (temp >= PNG_sRGB_INTENT_LAST)
      (void)png_icc_profile_error(png_ptr, NULL, name, temp,
         "intent outside defined range");

   /* At this point the tag table can't be checked because it hasn't necessarily
    * been loaded; however, various header fields can be checked.  These checks
    * are for values permitted by the PNG spec in an ICC profile; the PNG spec
    * restricts the profiles that can be passed in an iCCP chunk (they must be
    * appropriate to processing PNG data!)
    */

   /* Data checks (could be skipped).  These checks must be independent of the
    * version number; however, the version number doesn't accomodate changes in
    * the header fields (just the known tags and the interpretation of the
    * data.)
    */
   temp = png_get_uint_32(profile+36); /* signature 'ascp' */
   if (temp != 0x61637370)
      return png_icc_profile_error(png_ptr, colorspace, name, temp,
         "invalid signature");

   /* Currently the PCS illuminant/adopted white point (the computational
    * white point) are required to be D50,
    * however the profile contains a record of the illuminant so perhaps ICC
    * expects to be able to change this in the future (despite the rationale in
    * the introduction for using a fixed PCS adopted white.)  Consequently the
    * following is just a warning.
    */
   if (memcmp(profile+68, D50_nCIEXYZ, 12) != 0)
      (void)png_icc_profile_error(png_ptr, NULL, name, 0/*no tag value*/,
         "PCS illuminant is not D50");

   /* The PNG spec requires this:
    * "If the iCCP chunk is present, the image samples conform to the colour
    * space represented by the embedded ICC profile as defined by the
    * International Color Consortium [ICC]. The colour space of the ICC profile
    * shall be an RGB colour space for colour images (PNG colour types 2, 3, and
    * 6), or a greyscale colour space for greyscale images (PNG colour types 0
    * and 4)."
    *
    * This checking code ensures the embedded profile (on either read or write)
    * conforms to the specification requirements.  Notice that an ICC 'gray'
    * color-space profile contains the information to transform the monochrome
    * data to XYZ or L*a*b (according to which PCS the profile uses) and this
    * should be used in preference to the standard libpng K channel replication
    * into R, G and B channels.
    *
    * Previously it was suggested that an RGB profile on grayscale data could be
    * handled.  However it it is clear that using an RGB profile in this context
    * must be an error - there is no specification of what it means.  Thus it is
    * almost certainly more correct to ignore the profile.
    */
   temp = png_get_uint_32(profile+16); /* data colour space field */
   switch (temp)
   {
      case 0x52474220: /* 'RGB ' */
         if ((color_type & PNG_COLOR_MASK_COLOR) == 0)
            return png_icc_profile_error(png_ptr, colorspace, name, temp,
               "RGB color space not permitted on grayscale PNG");
         break;

      case 0x47524159: /* 'GRAY' */
         if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
            return png_icc_profile_error(png_ptr, colorspace, name, temp,
               "Gray color space not permitted on RGB PNG");
         break;

      default:
         return png_icc_profile_error(png_ptr, colorspace, name, temp,
            "invalid ICC profile color space");
   }

   /* It is up to the application to check that the profile class matches the
    * application requirements; the spec provides no guidance, but it's pretty
    * weird if the profile is not scanner ('scnr'), monitor ('mntr'), printer
    * ('prtr') or 'spac' (for generic color spaces).  Issue a warning in these
    * cases.  Issue an error for device link or abstract profiles - these don't
    * contain the records necessary to transform the color-space to anything
    * other than the target device (and not even that for an abstract profile).
    * Profiles of these classes may not be embedded in images.
    */
   temp = png_get_uint_32(profile+12); /* profile/device class */
   switch (temp)
   {
      case 0x73636e72: /* 'scnr' */
      case 0x6d6e7472: /* 'mntr' */
      case 0x70727472: /* 'prtr' */
      case 0x73706163: /* 'spac' */
         /* All supported */
         break;

      case 0x61627374: /* 'abst' */
         /* May not be embedded in an image */
         return png_icc_profile_error(png_ptr, colorspace, name, temp,
            "invalid embedded Abstract ICC profile");

      case 0x6c696e6b: /* 'link' */
         /* DeviceLink profiles cannot be interpreted in a non-device specific
          * fashion, if an app uses the AToB0Tag in the profile the results are
          * undefined unless the result is sent to the intended device,
          * therefore a DeviceLink profile should not be found embedded in a
          * PNG.
          */
         return png_icc_profile_error(png_ptr, colorspace, name, temp,
            "unexpected DeviceLink ICC profile class");

      case 0x6e6d636c: /* 'nmcl' */
         /* A NamedColor profile is also device specific, however it doesn't
          * contain an AToB0 tag that is open to misinterpretation.  Almost
          * certainly it will fail the tests below.
          */
         (void)png_icc_profile_error(png_ptr, NULL, name, temp,
            "unexpected NamedColor ICC profile class");
         break;

      default:
         /* To allow for future enhancements to the profile accept unrecognized
          * profile classes with a warning, these then hit the test below on the
          * tag content to ensure they are backward compatible with one of the
          * understood profiles.
          */
         (void)png_icc_profile_error(png_ptr, NULL, name, temp,
            "unrecognized ICC profile class");
         break;
   }

   /* For any profile other than a device link one the PCS must be encoded
    * either in XYZ or Lab.
    */
   temp = png_get_uint_32(profile+20);
   switch (temp)
   {
      case 0x58595a20: /* 'XYZ ' */
      case 0x4c616220: /* 'Lab ' */
         break;

      default:
         return png_icc_profile_error(png_ptr, colorspace, name, temp,
            "unexpected ICC PCS encoding");
   }

   return 1;
}

int /* PRIVATE */
png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace,
   png_const_charp name, png_uint_32 profile_length,
   png_const_bytep profile /* header plus whole tag table */)
{
   png_uint_32 tag_count = png_get_uint_32(profile+128);
   png_uint_32 itag;
   png_const_bytep tag = profile+132; /* The first tag */

   /* First scan all the tags in the table and add bits to the icc_info value
    * (temporarily in 'tags').
    */
   for (itag=0; itag < tag_count; ++itag, tag += 12)
   {
      png_uint_32 tag_id = png_get_uint_32(tag+0);
      png_uint_32 tag_start = png_get_uint_32(tag+4); /* must be aligned */
      png_uint_32 tag_length = png_get_uint_32(tag+8);/* not padded */

      /* The ICC specification does not exclude zero length tags, therefore the
       * start might actually be anywhere if there is no data, but this would be
       * a clear abuse of the intent of the standard so the start is checked for
       * being in range.  All defined tag types have an 8 byte header - a 4 byte
       * type signature then 0.
       */
      if ((tag_start & 3) != 0)
      {
         /* CNHP730S.icc shipped with Microsoft Windows 64 violates this, it is
          * only a warning here because libpng does not care about the
          * alignment.
          */
         (void)png_icc_profile_error(png_ptr, NULL, name, tag_id,
            "ICC profile tag start not a multiple of 4");
      }

      /* This is a hard error; potentially it can cause read outside the
       * profile.
       */
      if (tag_start > profile_length || tag_length > profile_length - tag_start)
         return png_icc_profile_error(png_ptr, colorspace, name, tag_id,
            "ICC profile tag outside profile");
   }

   return 1; /* success, maybe with warnings */
}

#ifdef PNG_sRGB_SUPPORTED
#if PNG_sRGB_PROFILE_CHECKS >= 0
/* Information about the known ICC sRGB profiles */
static const struct
{
   png_uint_32 adler, crc, length;
   png_uint_32 md5[4];
   png_byte    have_md5;
   png_byte    is_broken;
   png_uint_16 intent;

#  define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0)
#  define PNG_ICC_CHECKSUM(adler, crc, md5, intent, broke, date, length, fname)\
      { adler, crc, length, md5, broke, intent },

} png_sRGB_checks[] =
{
   /* This data comes from contrib/tools/checksum-icc run on downloads of
    * all four ICC sRGB profiles from www.color.org.
    */
   /* adler32, crc32, MD5[4], intent, date, length, file-name */
   PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9,
      PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0,
      "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")

   /* ICC sRGB v2 perceptual no black-compensation: */
   PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21,
      PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0,
      "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")

   PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae,
      PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0,
      "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")

   /* ICC sRGB v4 perceptual */
   PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812,
      PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0,
      "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")

   /* The following profiles have no known MD5 checksum. If there is a match
    * on the (empty) MD5 the other fields are used to attempt a match and
    * a warning is produced.  The first two of these profiles have a 'cprt' tag
    * which suggests that they were also made by Hewlett Packard.
    */
   PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce,
      PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0,
      "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")

   /* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not
    * match the D50 PCS illuminant in the header (it is in fact the D65 values,
    * so the white point is recorded as the un-adapted value.)  The profiles
    * below only differ in one byte - the intent - and are basically the same as
    * the previous profile except for the mediaWhitePointTag error and a missing
    * chromaticAdaptationTag.
    */
   PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552,
      PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/,
      "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual")

   PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d,
      PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/,
      "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative")
};

static int
png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,
   png_const_bytep profile, uLong adler)
{
   /* The quick check is to verify just the MD5 signature and trust the
    * rest of the data.  Because the profile has already been verified for
    * correctness this is safe.  png_colorspace_set_sRGB will check the 'intent'
    * field too, so if the profile has been edited with an intent not defined
    * by sRGB (but maybe defined by a later ICC specification) the read of
    * the profile will fail at that point.
    */

   png_uint_32 length = 0;
   png_uint_32 intent = 0x10000; /* invalid */
#if PNG_sRGB_PROFILE_CHECKS > 1
   uLong crc = 0; /* the value for 0 length data */
#endif
   unsigned int i;

#ifdef PNG_SET_OPTION_SUPPORTED
   /* First see if PNG_SKIP_sRGB_CHECK_PROFILE has been set to "on" */
   if (((png_ptr->options >> PNG_SKIP_sRGB_CHECK_PROFILE) & 3) ==
               PNG_OPTION_ON)
      return 0;
#endif

   for (i=0; i < (sizeof png_sRGB_checks) / (sizeof png_sRGB_checks[0]); ++i)
   {
      if (png_get_uint_32(profile+84) == png_sRGB_checks[i].md5[0] &&
         png_get_uint_32(profile+88) == png_sRGB_checks[i].md5[1] &&
         png_get_uint_32(profile+92) == png_sRGB_checks[i].md5[2] &&
         png_get_uint_32(profile+96) == png_sRGB_checks[i].md5[3])
      {
         /* This may be one of the old HP profiles without an MD5, in that
          * case we can only use the length and Adler32 (note that these
          * are not used by default if there is an MD5!)
          */
#        if PNG_sRGB_PROFILE_CHECKS == 0
            if (png_sRGB_checks[i].have_md5 != 0)
               return 1+png_sRGB_checks[i].is_broken;
#        endif

         /* Profile is unsigned or more checks have been configured in. */
         if (length == 0)
         {
            length = png_get_uint_32(profile);
            intent = png_get_uint_32(profile+64);
         }

         /* Length *and* intent must match */
         if (length == (png_uint_32) png_sRGB_checks[i].length &&
            intent == (png_uint_32) png_sRGB_checks[i].intent)
         {
            /* Now calculate the adler32 if not done already. */
            if (adler == 0)
            {
               adler = adler32(0, NULL, 0);
               adler = adler32(adler, profile, length);
            }

            if (adler == png_sRGB_checks[i].adler)
            {
               /* These basic checks suggest that the data has not been
                * modified, but if the check level is more than 1 perform
                * our own crc32 checksum on the data.
                */
#              if PNG_sRGB_PROFILE_CHECKS > 1
                  if (crc == 0)
                  {
                     crc = crc32(0, NULL, 0);
                     crc = crc32(crc, profile, length);
                  }

                  /* So this check must pass for the 'return' below to happen.
                   */
                  if (crc == png_sRGB_checks[i].crc)
#              endif
               {
                  if (png_sRGB_checks[i].is_broken != 0)
                  {
                     /* These profiles are known to have bad data that may cause
                      * problems if they are used, therefore attempt to
                      * discourage their use, skip the 'have_md5' warning below,
                      * which is made irrelevant by this error.
                      */
                     png_chunk_report(png_ptr, "known incorrect sRGB profile",
                        PNG_CHUNK_ERROR);
                  }

                  /* Warn that this being done; this isn't even an error since
                   * the profile is perfectly valid, but it would be nice if
                   * people used the up-to-date ones.
                   */
                  else if (png_sRGB_checks[i].have_md5 == 0)
                  {
                     png_chunk_report(png_ptr,
                        "out-of-date sRGB profile with no signature",
                        PNG_CHUNK_WARNING);
                  }

                  return 1+png_sRGB_checks[i].is_broken;
               }
            }

# if PNG_sRGB_PROFILE_CHECKS > 0
         /* The signature matched, but the profile had been changed in some
          * way.  This probably indicates a data error or uninformed hacking.
          * Fall through to "no match".
          */
         png_chunk_report(png_ptr,
             "Not recognizing known sRGB profile that has been edited",
             PNG_CHUNK_WARNING);
         break;
# endif
         }
      }
   }

   return 0; /* no match */
}
#endif /* PNG_sRGB_PROFILE_CHECKS >= 0 */

void /* PRIVATE */
png_icc_set_sRGB(png_const_structrp png_ptr,
   png_colorspacerp colorspace, png_const_bytep profile, uLong adler)
{
   /* Is this profile one of the known ICC sRGB profiles?  If it is, just set
    * the sRGB information.
    */
#if PNG_sRGB_PROFILE_CHECKS >= 0
   if (png_compare_ICC_profile_with_sRGB(png_ptr, profile, adler) != 0)
#endif
      (void)png_colorspace_set_sRGB(png_ptr, colorspace,
         (int)/*already checked*/png_get_uint_32(profile+64));
}
#endif /* sRGB */
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int /* PRIVATE */
2403 2404 2405
png_colorspace_set_ICC(png_const_structrp png_ptr, png_colorspacerp colorspace,
   png_const_charp name, png_uint_32 profile_length, png_const_bytep profile,
   int color_type)
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{
2407
   if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
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      return 0;

2410 2411 2412 2413 2414
   if (png_icc_check_length(png_ptr, colorspace, name, profile_length) != 0 &&
       png_icc_check_header(png_ptr, colorspace, name, profile_length, profile,
          color_type) != 0 &&
       png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,
          profile) != 0)
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   {
2416 2417 2418 2419 2420
#     ifdef PNG_sRGB_SUPPORTED
         /* If no sRGB support, don't try storing sRGB information */
         png_icc_set_sRGB(png_ptr, colorspace, profile, 0);
#     endif
      return 1;
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   }
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2423 2424 2425 2426
   /* Failure case */
   return 0;
}
#endif /* iCCP */
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2428 2429 2430 2431 2432 2433 2434
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
void /* PRIVATE */
png_colorspace_set_rgb_coefficients(png_structrp png_ptr)
{
   /* Set the rgb_to_gray coefficients from the colorspace. */
   if (png_ptr->rgb_to_gray_coefficients_set == 0 &&
      (png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
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   {
2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455
      /* png_set_background has not been called, get the coefficients from the Y
       * values of the colorspace colorants.
       */
      png_fixed_point r = png_ptr->colorspace.end_points_XYZ.red_Y;
      png_fixed_point g = png_ptr->colorspace.end_points_XYZ.green_Y;
      png_fixed_point b = png_ptr->colorspace.end_points_XYZ.blue_Y;
      png_fixed_point total = r+g+b;

      if (total > 0 &&
         r >= 0 && png_muldiv(&r, r, 32768, total) && r >= 0 && r <= 32768 &&
         g >= 0 && png_muldiv(&g, g, 32768, total) && g >= 0 && g <= 32768 &&
         b >= 0 && png_muldiv(&b, b, 32768, total) && b >= 0 && b <= 32768 &&
         r+g+b <= 32769)
      {
         /* We allow 0 coefficients here.  r+g+b may be 32769 if two or
          * all of the coefficients were rounded up.  Handle this by
          * reducing the *largest* coefficient by 1; this matches the
          * approach used for the default coefficients in pngrtran.c
          */
         int add = 0;
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2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470
         if (r+g+b > 32768)
            add = -1;
         else if (r+g+b < 32768)
            add = 1;

         if (add != 0)
         {
            if (g >= r && g >= b)
               g += add;
            else if (r >= g && r >= b)
               r += add;
            else
               b += add;
         }
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2472 2473 2474 2475
         /* Check for an internal error. */
         if (r+g+b != 32768)
            png_error(png_ptr,
               "internal error handling cHRM coefficients");
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2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489
         else
         {
            png_ptr->rgb_to_gray_red_coeff   = (png_uint_16)r;
            png_ptr->rgb_to_gray_green_coeff = (png_uint_16)g;
         }
      }

      /* This is a png_error at present even though it could be ignored -
       * it should never happen, but it is important that if it does, the
       * bug is fixed.
       */
      else
         png_error(png_ptr, "internal error handling cHRM->XYZ");
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   }
2491 2492
}
#endif /* READ_RGB_TO_GRAY */
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2494 2495 2496 2497 2498 2499 2500 2501
#endif /* COLORSPACE */

#ifdef __GNUC__
/* This exists solely to work round a warning from GNU C. */
static int /* PRIVATE */
png_gt(size_t a, size_t b)
{
    return a > b;
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}
2503 2504 2505
#else
#   define png_gt(a,b) ((a) > (b))
#endif
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void /* PRIVATE */
2508
png_check_IHDR(png_const_structrp png_ptr,
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   png_uint_32 width, png_uint_32 height, int bit_depth,
   int color_type, int interlace_type, int compression_type,
   int filter_type)
{
   int error = 0;

   /* Check for width and height valid values */
   if (width == 0)
   {
      png_warning(png_ptr, "Image width is zero in IHDR");
      error = 1;
   }
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2522
   if (width > PNG_UINT_31_MAX)
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   {
2524
      png_warning(png_ptr, "Invalid image width in IHDR");
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      error = 1;
   }

2528 2529 2530 2531 2532 2533
   if (png_gt(((width + 7) & (~7)),
       ((PNG_SIZE_MAX
           - 48        /* big_row_buf hack */
           - 1)        /* filter byte */
           / 8)        /* 8-byte RGBA pixels */
           - 1))       /* extra max_pixel_depth pad */
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   {
2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546
      /* The size of the row must be within the limits of this architecture.
       * Because the read code can perform arbitrary transformations the
       * maximum size is checked here.  Because the code in png_read_start_row
       * adds extra space "for safety's sake" in several places a conservative
       * limit is used here.
       *
       * NOTE: it would be far better to check the size that is actually used,
       * but the effect in the real world is minor and the changes are more
       * extensive, therefore much more dangerous and much more difficult to
       * write in a way that avoids compiler warnings.
       */
      png_warning(png_ptr, "Image width is too large for this architecture");
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      error = 1;
   }
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2550 2551 2552 2553 2554
#ifdef PNG_SET_USER_LIMITS_SUPPORTED
   if (width > png_ptr->user_width_max)
#else
   if (width > PNG_USER_WIDTH_MAX)
#endif
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   {
2556
      png_warning(png_ptr, "Image width exceeds user limit in IHDR");
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      error = 1;
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   }

2560
   if (height == 0)
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   {
2562
      png_warning(png_ptr, "Image height is zero in IHDR");
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      error = 1;
   }
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   if (height > PNG_UINT_31_MAX)
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   {
      png_warning(png_ptr, "Invalid image height in IHDR");
      error = 1;
   }
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2572 2573 2574 2575 2576 2577 2578 2579 2580
#ifdef PNG_SET_USER_LIMITS_SUPPORTED
   if (height > png_ptr->user_height_max)
#else
   if (height > PNG_USER_HEIGHT_MAX)
#endif
   {
      png_warning(png_ptr, "Image height exceeds user limit in IHDR");
      error = 1;
   }
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   /* Check other values */
   if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 &&
       bit_depth != 8 && bit_depth != 16)
   {
      png_warning(png_ptr, "Invalid bit depth in IHDR");
      error = 1;
   }

   if (color_type < 0 || color_type == 1 ||
       color_type == 5 || color_type > 6)
   {
      png_warning(png_ptr, "Invalid color type in IHDR");
      error = 1;
   }

   if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) ||
       ((color_type == PNG_COLOR_TYPE_RGB ||
         color_type == PNG_COLOR_TYPE_GRAY_ALPHA ||
         color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8))
   {
      png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR");
      error = 1;
   }

   if (interlace_type >= PNG_INTERLACE_LAST)
   {
      png_warning(png_ptr, "Unknown interlace method in IHDR");
      error = 1;
   }

   if (compression_type != PNG_COMPRESSION_TYPE_BASE)
   {
      png_warning(png_ptr, "Unknown compression method in IHDR");
      error = 1;
   }

2618
#ifdef PNG_MNG_FEATURES_SUPPORTED
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   /* Accept filter_method 64 (intrapixel differencing) only if
    * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
    * 2. Libpng did not read a PNG signature (this filter_method is only
    *    used in PNG datastreams that are embedded in MNG datastreams) and
    * 3. The application called png_permit_mng_features with a mask that
    *    included PNG_FLAG_MNG_FILTER_64 and
    * 4. The filter_method is 64 and
    * 5. The color_type is RGB or RGBA
    */
2628 2629
   if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 &&
       png_ptr->mng_features_permitted != 0)
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      png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");

   if (filter_type != PNG_FILTER_TYPE_BASE)
   {
2634
      if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
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          (filter_type == PNG_INTRAPIXEL_DIFFERENCING) &&
          ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) &&
          (color_type == PNG_COLOR_TYPE_RGB ||
          color_type == PNG_COLOR_TYPE_RGB_ALPHA)))
      {
         png_warning(png_ptr, "Unknown filter method in IHDR");
         error = 1;
      }

2644
      if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0)
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      {
         png_warning(png_ptr, "Invalid filter method in IHDR");
         error = 1;
      }
   }

2651
#else
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   if (filter_type != PNG_FILTER_TYPE_BASE)
   {
      png_warning(png_ptr, "Unknown filter method in IHDR");
      error = 1;
   }
2657
#endif
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   if (error == 1)
      png_error(png_ptr, "Invalid IHDR data");
}

#if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)
/* ASCII to fp functions */
/* Check an ASCII formated floating point value, see the more detailed
 * comments in pngpriv.h
 */
/* The following is used internally to preserve the sticky flags */
#define png_fp_add(state, flags) ((state) |= (flags))
#define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))

int /* PRIVATE */
png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
   png_size_tp whereami)
{
   int state = *statep;
   png_size_t i = *whereami;

   while (i < size)
   {
      int type;
      /* First find the type of the next character */
      switch (string[i])
      {
      case 43:  type = PNG_FP_SAW_SIGN;                   break;
      case 45:  type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break;
      case 46:  type = PNG_FP_SAW_DOT;                    break;
      case 48:  type = PNG_FP_SAW_DIGIT;                  break;
      case 49: case 50: case 51: case 52:
      case 53: case 54: case 55: case 56:
      case 57:  type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break;
      case 69:
      case 101: type = PNG_FP_SAW_E;                      break;
      default:  goto PNG_FP_End;
      }

      /* Now deal with this type according to the current
       * state, the type is arranged to not overlap the
       * bits of the PNG_FP_STATE.
       */
      switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY))
      {
      case PNG_FP_INTEGER + PNG_FP_SAW_SIGN:
2704
         if ((state & PNG_FP_SAW_ANY) != 0)
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            goto PNG_FP_End; /* not a part of the number */

         png_fp_add(state, type);
         break;

      case PNG_FP_INTEGER + PNG_FP_SAW_DOT:
         /* Ok as trailer, ok as lead of fraction. */
2712
         if ((state & PNG_FP_SAW_DOT) != 0) /* two dots */
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            goto PNG_FP_End;

2715
         else if ((state & PNG_FP_SAW_DIGIT) != 0) /* trailing dot? */
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            png_fp_add(state, type);

         else
            png_fp_set(state, PNG_FP_FRACTION | type);

         break;

      case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT:
2724
         if ((state & PNG_FP_SAW_DOT) != 0) /* delayed fraction */
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            png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);

         png_fp_add(state, type | PNG_FP_WAS_VALID);

         break;

      case PNG_FP_INTEGER + PNG_FP_SAW_E:
         if ((state & PNG_FP_SAW_DIGIT) == 0)
            goto PNG_FP_End;

         png_fp_set(state, PNG_FP_EXPONENT);

         break;

   /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:
         goto PNG_FP_End; ** no sign in fraction */

   /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:
         goto PNG_FP_End; ** Because SAW_DOT is always set */

      case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT:
         png_fp_add(state, type | PNG_FP_WAS_VALID);
         break;

      case PNG_FP_FRACTION + PNG_FP_SAW_E:
         /* This is correct because the trailing '.' on an
          * integer is handled above - so we can only get here
          * with the sequence ".E" (with no preceding digits).
          */
         if ((state & PNG_FP_SAW_DIGIT) == 0)
            goto PNG_FP_End;

         png_fp_set(state, PNG_FP_EXPONENT);

         break;

      case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN:
2762
         if ((state & PNG_FP_SAW_ANY) != 0)
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            goto PNG_FP_End; /* not a part of the number */

         png_fp_add(state, PNG_FP_SAW_SIGN);

         break;

   /* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT:
         goto PNG_FP_End; */

      case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT:
         png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID);

         break;

   /* case PNG_FP_EXPONEXT + PNG_FP_SAW_E:
         goto PNG_FP_End; */

      default: goto PNG_FP_End; /* I.e. break 2 */
      }

      /* The character seems ok, continue. */
      ++i;
   }

PNG_FP_End:
   /* Here at the end, update the state and return the correct
    * return code.
    */
   *statep = state;
   *whereami = i;

   return (state & PNG_FP_SAW_DIGIT) != 0;
}


/* The same but for a complete string. */
int
png_check_fp_string(png_const_charp string, png_size_t size)
{
   int        state=0;
   png_size_t char_index=0;

2805
   if (png_check_fp_number(string, size, &state, &char_index) != 0 &&
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      (char_index == size || string[char_index] == 0))
      return state /* must be non-zero - see above */;

   return 0; /* i.e. fail */
}
2811
#endif /* pCAL || sCAL */
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2813
#ifdef PNG_sCAL_SUPPORTED
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#  ifdef PNG_FLOATING_POINT_SUPPORTED
/* Utility used below - a simple accurate power of ten from an integral
 * exponent.
 */
static double
png_pow10(int power)
{
   int recip = 0;
   double d = 1;

   /* Handle negative exponent with a reciprocal at the end because
    * 10 is exact whereas .1 is inexact in base 2
    */
   if (power < 0)
   {
      if (power < DBL_MIN_10_EXP) return 0;
      recip = 1, power = -power;
   }

   if (power > 0)
   {
      /* Decompose power bitwise. */
      double mult = 10;
      do
      {
         if (power & 1) d *= mult;
         mult *= mult;
         power >>= 1;
      }
      while (power > 0);

2845
      if (recip != 0) d = 1/d;
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   }
   /* else power is 0 and d is 1 */

   return d;
}

/* Function to format a floating point value in ASCII with a given
 * precision.
 */
void /* PRIVATE */
2856
png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
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    double fp, unsigned int precision)
{
   /* We use standard functions from math.h, but not printf because
    * that would require stdio.  The caller must supply a buffer of
    * sufficient size or we will png_error.  The tests on size and
    * the space in ascii[] consumed are indicated below.
    */
   if (precision < 1)
      precision = DBL_DIG;

   /* Enforce the limit of the implementation precision too. */
   if (precision > DBL_DIG+1)
      precision = DBL_DIG+1;

   /* Basic sanity checks */
   if (size >= precision+5) /* See the requirements below. */
   {
      if (fp < 0)
      {
         fp = -fp;
         *ascii++ = 45; /* '-'  PLUS 1 TOTAL 1 */
         --size;
      }

      if (fp >= DBL_MIN && fp <= DBL_MAX)
      {
2883
         int exp_b10;   /* A base 10 exponent */
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         double base;   /* 10^exp_b10 */

         /* First extract a base 10 exponent of the number,
          * the calculation below rounds down when converting
          * from base 2 to base 10 (multiply by log10(2) -
          * 0.3010, but 77/256 is 0.3008, so exp_b10 needs to
          * be increased.  Note that the arithmetic shift
          * performs a floor() unlike C arithmetic - using a
          * C multiply would break the following for negative
          * exponents.
          */
         (void)frexp(fp, &exp_b10); /* exponent to base 2 */

         exp_b10 = (exp_b10 * 77) >> 8; /* <= exponent to base 10 */

         /* Avoid underflow here. */
         base = png_pow10(exp_b10); /* May underflow */

         while (base < DBL_MIN || base < fp)
         {
            /* And this may overflow. */
            double test = png_pow10(exp_b10+1);

            if (test <= DBL_MAX)
               ++exp_b10, base = test;

            else
               break;
         }

         /* Normalize fp and correct exp_b10, after this fp is in the
          * range [.1,1) and exp_b10 is both the exponent and the digit
          * *before* which the decimal point should be inserted
          * (starting with 0 for the first digit).  Note that this
          * works even if 10^exp_b10 is out of range because of the
          * test on DBL_MAX above.
          */
         fp /= base;
         while (fp >= 1) fp /= 10, ++exp_b10;

         /* Because of the code above fp may, at this point, be
          * less than .1, this is ok because the code below can
          * handle the leading zeros this generates, so no attempt
          * is made to correct that here.
          */

         {
2931
            unsigned int czero, clead, cdigits;
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            char exponent[10];

            /* Allow up to two leading zeros - this will not lengthen
             * the number compared to using E-n.
             */
            if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */
            {
               czero = -exp_b10; /* PLUS 2 digits: TOTAL 3 */
               exp_b10 = 0;      /* Dot added below before first output. */
            }
            else
               czero = 0;    /* No zeros to add */

            /* Generate the digit list, stripping trailing zeros and
             * inserting a '.' before a digit if the exponent is 0.
             */
            clead = czero; /* Count of leading zeros */
            cdigits = 0;   /* Count of digits in list. */

            do
            {
               double d;

               fp *= 10;
               /* Use modf here, not floor and subtract, so that
                * the separation is done in one step.  At the end
                * of the loop don't break the number into parts so
                * that the final digit is rounded.
                */
2961
               if (cdigits+czero+1 < precision+clead)
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                  fp = modf(fp, &d);

               else
               {
                  d = floor(fp + .5);

                  if (d > 9)
                  {
                     /* Rounding up to 10, handle that here. */
                     if (czero > 0)
                     {
                        --czero, d = 1;
                        if (cdigits == 0) --clead;
                     }
                     else
                     {
                        while (cdigits > 0 && d > 9)
                        {
                           int ch = *--ascii;

                           if (exp_b10 != (-1))
                              ++exp_b10;

                           else if (ch == 46)
                           {
                              ch = *--ascii, ++size;
                              /* Advance exp_b10 to '1', so that the
                               * decimal point happens after the
                               * previous digit.
                               */
                              exp_b10 = 1;
                           }

                           --cdigits;
                           d = ch - 47;  /* I.e. 1+(ch-48) */
                        }

                        /* Did we reach the beginning? If so adjust the
                         * exponent but take into account the leading
                         * decimal point.
                         */
                        if (d > 9)  /* cdigits == 0 */
                        {
                           if (exp_b10 == (-1))
                           {
                              /* Leading decimal point (plus zeros?), if
                               * we lose the decimal point here it must
                               * be reentered below.
                               */
                              int ch = *--ascii;

                              if (ch == 46)
                                 ++size, exp_b10 = 1;

                              /* Else lost a leading zero, so 'exp_b10' is
                               * still ok at (-1)
                               */
                           }
                           else
                              ++exp_b10;

                           /* In all cases we output a '1' */
                           d = 1;
                        }
                     }
                  }
                  fp = 0; /* Guarantees termination below. */
               }

               if (d == 0)
               {
                  ++czero;
                  if (cdigits == 0) ++clead;
               }
               else
               {
                  /* Included embedded zeros in the digit count. */
                  cdigits += czero - clead;
                  clead = 0;

                  while (czero > 0)
                  {
                     /* exp_b10 == (-1) means we just output the decimal
                      * place - after the DP don't adjust 'exp_b10' any
                      * more!
                      */
                     if (exp_b10 != (-1))
                     {
                        if (exp_b10 == 0) *ascii++ = 46, --size;
                        /* PLUS 1: TOTAL 4 */
                        --exp_b10;
                     }
                     *ascii++ = 48, --czero;
                  }

                  if (exp_b10 != (-1))
                  {
3059 3060 3061
                     if (exp_b10 == 0)
                        *ascii++ = 46, --size; /* counted above */

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                     --exp_b10;
                  }
                  *ascii++ = (char)(48 + (int)d), ++cdigits;
               }
            }
3067
            while (cdigits+czero < precision+clead && fp > DBL_MIN);
B
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            /* The total output count (max) is now 4+precision */

            /* Check for an exponent, if we don't need one we are
             * done and just need to terminate the string.  At
             * this point exp_b10==(-1) is effectively if flag - it got
3074
             * to '-1' because of the decrement after outputting
B
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3075 3076 3077 3078 3079 3080 3081
             * the decimal point above (the exponent required is
             * *not* -1!)
             */
            if (exp_b10 >= (-1) && exp_b10 <= 2)
            {
               /* The following only happens if we didn't output the
                * leading zeros above for negative exponent, so this
3082
                * doesn't add to the digit requirement.  Note that the
B
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3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105
                * two zeros here can only be output if the two leading
                * zeros were *not* output, so this doesn't increase
                * the output count.
                */
               while (--exp_b10 >= 0) *ascii++ = 48;

               *ascii = 0;

               /* Total buffer requirement (including the '\0') is
                * 5+precision - see check at the start.
                */
               return;
            }

            /* Here if an exponent is required, adjust size for
             * the digits we output but did not count.  The total
             * digit output here so far is at most 1+precision - no
             * decimal point and no leading or trailing zeros have
             * been output.
             */
            size -= cdigits;

            *ascii++ = 69, --size;    /* 'E': PLUS 1 TOTAL 2+precision */
3106 3107 3108 3109 3110

            /* The following use of an unsigned temporary avoids ambiguities in
             * the signed arithmetic on exp_b10 and permits GCC at least to do
             * better optimization.
             */
B
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3111
            {
3112 3113 3114 3115 3116 3117 3118 3119 3120 3121
               unsigned int uexp_b10;

               if (exp_b10 < 0)
               {
                  *ascii++ = 45, --size; /* '-': PLUS 1 TOTAL 3+precision */
                  uexp_b10 = -exp_b10;
               }

               else
                  uexp_b10 = exp_b10;
A
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3122

3123
               cdigits = 0;
A
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3124

3125 3126 3127 3128 3129
               while (uexp_b10 > 0)
               {
                  exponent[cdigits++] = (char)(48 + uexp_b10 % 10);
                  uexp_b10 /= 10;
               }
B
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3130 3131 3132 3133 3134
            }

            /* Need another size check here for the exponent digits, so
             * this need not be considered above.
             */
3135
            if (size > cdigits)
B
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3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170
            {
               while (cdigits > 0) *ascii++ = exponent[--cdigits];

               *ascii = 0;

               return;
            }
         }
      }
      else if (!(fp >= DBL_MIN))
      {
         *ascii++ = 48; /* '0' */
         *ascii = 0;
         return;
      }
      else
      {
         *ascii++ = 105; /* 'i' */
         *ascii++ = 110; /* 'n' */
         *ascii++ = 102; /* 'f' */
         *ascii = 0;
         return;
      }
   }

   /* Here on buffer too small. */
   png_error(png_ptr, "ASCII conversion buffer too small");
}

#  endif /* FLOATING_POINT */

#  ifdef PNG_FIXED_POINT_SUPPORTED
/* Function to format a fixed point value in ASCII.
 */
void /* PRIVATE */
3171 3172
png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii,
    png_size_t size, png_fixed_point fp)
B
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3173 3174 3175 3176 3177 3178 3179 3180 3181 3182
{
   /* Require space for 10 decimal digits, a decimal point, a minus sign and a
    * trailing \0, 13 characters:
    */
   if (size > 12)
   {
      png_uint_32 num;

      /* Avoid overflow here on the minimum integer. */
      if (fp < 0)
3183
         *ascii++ = 45, num = -fp;
B
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3184 3185 3186
      else
         num = fp;

3187
      if (num <= 0x80000000) /* else overflowed */
B
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3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238
      {
         unsigned int ndigits = 0, first = 16 /* flag value */;
         char digits[10];

         while (num)
         {
            /* Split the low digit off num: */
            unsigned int tmp = num/10;
            num -= tmp*10;
            digits[ndigits++] = (char)(48 + num);
            /* Record the first non-zero digit, note that this is a number
             * starting at 1, it's not actually the array index.
             */
            if (first == 16 && num > 0)
               first = ndigits;
            num = tmp;
         }

         if (ndigits > 0)
         {
            while (ndigits > 5) *ascii++ = digits[--ndigits];
            /* The remaining digits are fractional digits, ndigits is '5' or
             * smaller at this point.  It is certainly not zero.  Check for a
             * non-zero fractional digit:
             */
            if (first <= 5)
            {
               unsigned int i;
               *ascii++ = 46; /* decimal point */
               /* ndigits may be <5 for small numbers, output leading zeros
                * then ndigits digits to first:
                */
               i = 5;
               while (ndigits < i) *ascii++ = 48, --i;
               while (ndigits >= first) *ascii++ = digits[--ndigits];
               /* Don't output the trailing zeros! */
            }
         }
         else
            *ascii++ = 48;

         /* And null terminate the string: */
         *ascii = 0;
         return;
      }
   }

   /* Here on buffer too small. */
   png_error(png_ptr, "ASCII conversion buffer too small");
}
#   endif /* FIXED_POINT */
3239
#endif /* SCAL */
B
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3240 3241

#if defined(PNG_FLOATING_POINT_SUPPORTED) && \
3242 3243 3244 3245 3246 3247
   !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
   (defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \
   defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \
   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \
   (defined(PNG_sCAL_SUPPORTED) && \
   defined(PNG_FLOATING_ARITHMETIC_SUPPORTED))
B
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3248
png_fixed_point
3249
png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text)
B
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3250 3251 3252 3253 3254 3255
{
   double r = floor(100000 * fp + .5);

   if (r > 2147483647. || r < -2147483648.)
      png_fixed_error(png_ptr, text);

3256 3257 3258 3259
#  ifndef PNG_ERROR_TEXT_SUPPORTED
   PNG_UNUSED(text)
#  endif

B
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   return (png_fixed_point)r;
}
#endif

3264 3265
#if defined(PNG_GAMMA_SUPPORTED) || defined(PNG_COLORSPACE_SUPPORTED) ||\
    defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED)
B
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/* muldiv functions */
/* This API takes signed arguments and rounds the result to the nearest
 * integer (or, for a fixed point number - the standard argument - to
 * the nearest .00001).  Overflow and divide by zero are signalled in
 * the result, a boolean - true on success, false on overflow.
 */
int
png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,
    png_int_32 divisor)
{
   /* Return a * times / divisor, rounded. */
   if (divisor != 0)
   {
      if (a == 0 || times == 0)
      {
         *res = 0;
         return 1;
      }
      else
      {
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
         double r = a;
         r *= times;
         r /= divisor;
         r = floor(r+.5);

         /* A png_fixed_point is a 32-bit integer. */
         if (r <= 2147483647. && r >= -2147483648.)
         {
            *res = (png_fixed_point)r;
            return 1;
         }
#else
         int negative = 0;
         png_uint_32 A, T, D;
         png_uint_32 s16, s32, s00;

         if (a < 0)
            negative = 1, A = -a;
         else
            A = a;

         if (times < 0)
            negative = !negative, T = -times;
         else
            T = times;

         if (divisor < 0)
            negative = !negative, D = -divisor;
         else
            D = divisor;

         /* Following can't overflow because the arguments only
          * have 31 bits each, however the result may be 32 bits.
          */
         s16 = (A >> 16) * (T & 0xffff) +
                           (A & 0xffff) * (T >> 16);
         /* Can't overflow because the a*times bit is only 30
          * bits at most.
          */
         s32 = (A >> 16) * (T >> 16) + (s16 >> 16);
         s00 = (A & 0xffff) * (T & 0xffff);

         s16 = (s16 & 0xffff) << 16;
         s00 += s16;

         if (s00 < s16)
            ++s32; /* carry */

         if (s32 < D) /* else overflow */
         {
            /* s32.s00 is now the 64-bit product, do a standard
             * division, we know that s32 < D, so the maximum
             * required shift is 31.
             */
            int bitshift = 32;
            png_fixed_point result = 0; /* NOTE: signed */

            while (--bitshift >= 0)
            {
               png_uint_32 d32, d00;

               if (bitshift > 0)
                  d32 = D >> (32-bitshift), d00 = D << bitshift;

               else
                  d32 = 0, d00 = D;

               if (s32 > d32)
               {
                  if (s00 < d00) --s32; /* carry */
                  s32 -= d32, s00 -= d00, result += 1<<bitshift;
               }

               else
                  if (s32 == d32 && s00 >= d00)
                     s32 = 0, s00 -= d00, result += 1<<bitshift;
            }

            /* Handle the rounding. */
            if (s00 >= (D >> 1))
               ++result;

3369
            if (negative != 0)
B
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3370 3371 3372
               result = -result;

            /* Check for overflow. */
3373 3374
            if ((negative != 0 && result <= 0) ||
                (negative == 0 && result >= 0))
B
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3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392
            {
               *res = result;
               return 1;
            }
         }
#endif
      }
   }

   return 0;
}
#endif /* READ_GAMMA || INCH_CONVERSIONS */

#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)
/* The following is for when the caller doesn't much care about the
 * result.
 */
png_fixed_point
3393
png_muldiv_warn(png_const_structrp png_ptr, png_fixed_point a, png_int_32 times,
B
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3394 3395 3396 3397
    png_int_32 divisor)
{
   png_fixed_point result;

3398
   if (png_muldiv(&result, a, times, divisor) != 0)
B
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      return result;

   png_warning(png_ptr, "fixed point overflow ignored");
   return 0;
}
#endif

3406
#ifdef PNG_GAMMA_SUPPORTED /* more fixed point functions for gamma */
B
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/* Calculate a reciprocal, return 0 on div-by-zero or overflow. */
png_fixed_point
png_reciprocal(png_fixed_point a)
{
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
   double r = floor(1E10/a+.5);

   if (r <= 2147483647. && r >= -2147483648.)
      return (png_fixed_point)r;
#else
   png_fixed_point res;

3419
   if (png_muldiv(&res, 100000, 100000, a) != 0)
B
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      return res;
#endif

   return 0; /* error/overflow */
}

3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438
/* This is the shared test on whether a gamma value is 'significant' - whether
 * it is worth doing gamma correction.
 */
int /* PRIVATE */
png_gamma_significant(png_fixed_point gamma_val)
{
   return gamma_val < PNG_FP_1 - PNG_GAMMA_THRESHOLD_FIXED ||
       gamma_val > PNG_FP_1 + PNG_GAMMA_THRESHOLD_FIXED;
}
#endif

#ifdef PNG_READ_GAMMA_SUPPORTED
#ifdef PNG_16BIT_SUPPORTED
B
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3439 3440 3441 3442 3443
/* A local convenience routine. */
static png_fixed_point
png_product2(png_fixed_point a, png_fixed_point b)
{
   /* The required result is 1/a * 1/b; the following preserves accuracy. */
A
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3444
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
B
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3445 3446 3447 3448 3449 3450
   double r = a * 1E-5;
   r *= b;
   r = floor(r+.5);

   if (r <= 2147483647. && r >= -2147483648.)
      return (png_fixed_point)r;
A
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3451
#else
B
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3452 3453
   png_fixed_point res;

3454
   if (png_muldiv(&res, a, b, 100000) != 0)
B
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3455
      return res;
A
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3456
#endif
B
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3457 3458 3459

   return 0; /* overflow */
}
3460
#endif /* 16BIT */
B
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3461 3462 3463 3464 3465 3466 3467

/* The inverse of the above. */
png_fixed_point
png_reciprocal2(png_fixed_point a, png_fixed_point b)
{
   /* The required result is 1/a * 1/b; the following preserves accuracy. */
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3468 3469 3470 3471 3472
   if (a != 0 && b != 0)
   {
      double r = 1E15/a;
      r /= b;
      r = floor(r+.5);
B
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3473

3474 3475 3476
      if (r <= 2147483647. && r >= -2147483648.)
         return (png_fixed_point)r;
   }
B
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#else
   /* This may overflow because the range of png_fixed_point isn't symmetric,
    * but this API is only used for the product of file and screen gamma so it
    * doesn't matter that the smallest number it can produce is 1/21474, not
    * 1/100000
    */
   png_fixed_point res = png_product2(a, b);

   if (res != 0)
      return png_reciprocal(res);
#endif

   return 0; /* overflow */
}
#endif /* READ_GAMMA */

#ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */
#ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* Fixed point gamma.
3496 3497 3498
 *
 * The code to calculate the tables used below can be found in the shell script
 * contrib/tools/intgamma.sh
B
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 *
 * To calculate gamma this code implements fast log() and exp() calls using only
 * fixed point arithmetic.  This code has sufficient precision for either 8-bit
 * or 16-bit sample values.
 *
 * The tables used here were calculated using simple 'bc' programs, but C double
3505
 * precision floating point arithmetic would work fine.
B
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 *
 * 8-bit log table
 *   This is a table of -log(value/255)/log(2) for 'value' in the range 128 to
 *   255, so it's the base 2 logarithm of a normalized 8-bit floating point
 *   mantissa.  The numbers are 32-bit fractions.
 */
3512
static const png_uint_32
B
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png_8bit_l2[128] =
{
   4270715492U, 4222494797U, 4174646467U, 4127164793U, 4080044201U, 4033279239U,
   3986864580U, 3940795015U, 3895065449U, 3849670902U, 3804606499U, 3759867474U,
   3715449162U, 3671346997U, 3627556511U, 3584073329U, 3540893168U, 3498011834U,
   3455425220U, 3413129301U, 3371120137U, 3329393864U, 3287946700U, 3246774933U,
   3205874930U, 3165243125U, 3124876025U, 3084770202U, 3044922296U, 3005329011U,
   2965987113U, 2926893432U, 2888044853U, 2849438323U, 2811070844U, 2772939474U,
   2735041326U, 2697373562U, 2659933400U, 2622718104U, 2585724991U, 2548951424U,
   2512394810U, 2476052606U, 2439922311U, 2404001468U, 2368287663U, 2332778523U,
   2297471715U, 2262364947U, 2227455964U, 2192742551U, 2158222529U, 2123893754U,
   2089754119U, 2055801552U, 2022034013U, 1988449497U, 1955046031U, 1921821672U,
   1888774511U, 1855902668U, 1823204291U, 1790677560U, 1758320682U, 1726131893U,
   1694109454U, 1662251657U, 1630556815U, 1599023271U, 1567649391U, 1536433567U,
   1505374214U, 1474469770U, 1443718700U, 1413119487U, 1382670639U, 1352370686U,
   1322218179U, 1292211689U, 1262349810U, 1232631153U, 1203054352U, 1173618059U,
   1144320946U, 1115161701U, 1086139034U, 1057251672U, 1028498358U, 999877854U,
   971388940U, 943030410U, 914801076U, 886699767U, 858725327U, 830876614U,
   803152505U, 775551890U, 748073672U, 720716771U, 693480120U, 666362667U,
   639363374U, 612481215U, 585715177U, 559064263U, 532527486U, 506103872U,
   479792461U, 453592303U, 427502463U, 401522014U, 375650043U, 349885648U,
   324227938U, 298676034U, 273229066U, 247886176U, 222646516U, 197509248U,
   172473545U, 147538590U, 122703574U, 97967701U, 73330182U, 48790236U,
   24347096U, 0U
3537

B
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3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558
#if 0
   /* The following are the values for 16-bit tables - these work fine for the
    * 8-bit conversions but produce very slightly larger errors in the 16-bit
    * log (about 1.2 as opposed to 0.7 absolute error in the final value).  To
    * use these all the shifts below must be adjusted appropriately.
    */
   65166, 64430, 63700, 62976, 62257, 61543, 60835, 60132, 59434, 58741, 58054,
   57371, 56693, 56020, 55352, 54689, 54030, 53375, 52726, 52080, 51439, 50803,
   50170, 49542, 48918, 48298, 47682, 47070, 46462, 45858, 45257, 44661, 44068,
   43479, 42894, 42312, 41733, 41159, 40587, 40020, 39455, 38894, 38336, 37782,
   37230, 36682, 36137, 35595, 35057, 34521, 33988, 33459, 32932, 32408, 31887,
   31369, 30854, 30341, 29832, 29325, 28820, 28319, 27820, 27324, 26830, 26339,
   25850, 25364, 24880, 24399, 23920, 23444, 22970, 22499, 22029, 21562, 21098,
   20636, 20175, 19718, 19262, 18808, 18357, 17908, 17461, 17016, 16573, 16132,
   15694, 15257, 14822, 14390, 13959, 13530, 13103, 12678, 12255, 11834, 11415,
   10997, 10582, 10168, 9756, 9346, 8937, 8531, 8126, 7723, 7321, 6921, 6523,
   6127, 5732, 5339, 4947, 4557, 4169, 3782, 3397, 3014, 2632, 2251, 1872, 1495,
   1119, 744, 372
#endif
};

3559
static png_int_32
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3560 3561 3562 3563 3564 3565
png_log8bit(unsigned int x)
{
   unsigned int lg2 = 0;
   /* Each time 'x' is multiplied by 2, 1 must be subtracted off the final log,
    * because the log is actually negate that means adding 1.  The final
    * returned value thus has the range 0 (for 255 input) to 7.994 (for 1
3566
    * input), return -1 for the overflow (log 0) case, - so the result is
B
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3567 3568 3569
    * always at most 19 bits.
    */
   if ((x &= 0xff) == 0)
3570
      return -1;
B
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3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614

   if ((x & 0xf0) == 0)
      lg2  = 4, x <<= 4;

   if ((x & 0xc0) == 0)
      lg2 += 2, x <<= 2;

   if ((x & 0x80) == 0)
      lg2 += 1, x <<= 1;

   /* result is at most 19 bits, so this cast is safe: */
   return (png_int_32)((lg2 << 16) + ((png_8bit_l2[x-128]+32768)>>16));
}

/* The above gives exact (to 16 binary places) log2 values for 8-bit images,
 * for 16-bit images we use the most significant 8 bits of the 16-bit value to
 * get an approximation then multiply the approximation by a correction factor
 * determined by the remaining up to 8 bits.  This requires an additional step
 * in the 16-bit case.
 *
 * We want log2(value/65535), we have log2(v'/255), where:
 *
 *    value = v' * 256 + v''
 *          = v' * f
 *
 * So f is value/v', which is equal to (256+v''/v') since v' is in the range 128
 * to 255 and v'' is in the range 0 to 255 f will be in the range 256 to less
 * than 258.  The final factor also needs to correct for the fact that our 8-bit
 * value is scaled by 255, whereas the 16-bit values must be scaled by 65535.
 *
 * This gives a final formula using a calculated value 'x' which is value/v' and
 * scaling by 65536 to match the above table:
 *
 *   log2(x/257) * 65536
 *
 * Since these numbers are so close to '1' we can use simple linear
 * interpolation between the two end values 256/257 (result -368.61) and 258/257
 * (result 367.179).  The values used below are scaled by a further 64 to give
 * 16-bit precision in the interpolation:
 *
 * Start (256): -23591
 * Zero  (257):      0
 * End   (258):  23499
 */
3615 3616
#ifdef PNG_16BIT_SUPPORTED
static png_int_32
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png_log16bit(png_uint_32 x)
{
   unsigned int lg2 = 0;

   /* As above, but now the input has 16 bits. */
   if ((x &= 0xffff) == 0)
3623
      return -1;
B
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3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665

   if ((x & 0xff00) == 0)
      lg2  = 8, x <<= 8;

   if ((x & 0xf000) == 0)
      lg2 += 4, x <<= 4;

   if ((x & 0xc000) == 0)
      lg2 += 2, x <<= 2;

   if ((x & 0x8000) == 0)
      lg2 += 1, x <<= 1;

   /* Calculate the base logarithm from the top 8 bits as a 28-bit fractional
    * value.
    */
   lg2 <<= 28;
   lg2 += (png_8bit_l2[(x>>8)-128]+8) >> 4;

   /* Now we need to interpolate the factor, this requires a division by the top
    * 8 bits.  Do this with maximum precision.
    */
   x = ((x << 16) + (x >> 9)) / (x >> 8);

   /* Since we divided by the top 8 bits of 'x' there will be a '1' at 1<<24,
    * the value at 1<<16 (ignoring this) will be 0 or 1; this gives us exactly
    * 16 bits to interpolate to get the low bits of the result.  Round the
    * answer.  Note that the end point values are scaled by 64 to retain overall
    * precision and that 'lg2' is current scaled by an extra 12 bits, so adjust
    * the overall scaling by 6-12.  Round at every step.
    */
   x -= 1U << 24;

   if (x <= 65536U) /* <= '257' */
      lg2 += ((23591U * (65536U-x)) + (1U << (16+6-12-1))) >> (16+6-12);

   else
      lg2 -= ((23499U * (x-65536U)) + (1U << (16+6-12-1))) >> (16+6-12);

   /* Safe, because the result can't have more than 20 bits: */
   return (png_int_32)((lg2 + 2048) >> 12);
}
3666
#endif /* 16BIT */
B
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3667 3668 3669 3670 3671 3672

/* The 'exp()' case must invert the above, taking a 20-bit fixed point
 * logarithmic value and returning a 16 or 8-bit number as appropriate.  In
 * each case only the low 16 bits are relevant - the fraction - since the
 * integer bits (the top 4) simply determine a shift.
 *
3673 3674
 * The worst case is the 16-bit distinction between 65535 and 65534. This
 * requires perhaps spurious accuracy in the decoding of the logarithm to
B
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3675 3676 3677 3678 3679 3680 3681
 * distinguish log2(65535/65534.5) - 10^-5 or 17 bits.  There is little chance
 * of getting this accuracy in practice.
 *
 * To deal with this the following exp() function works out the exponent of the
 * frational part of the logarithm by using an accurate 32-bit value from the
 * top four fractional bits then multiplying in the remaining bits.
 */
3682
static const png_uint_32
B
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3683 3684 3685 3686 3687 3688 3689 3690 3691
png_32bit_exp[16] =
{
   /* NOTE: the first entry is deliberately set to the maximum 32-bit value. */
   4294967295U, 4112874773U, 3938502376U, 3771522796U, 3611622603U, 3458501653U,
   3311872529U, 3171459999U, 3037000500U, 2908241642U, 2784941738U, 2666869345U,
   2553802834U, 2445529972U, 2341847524U, 2242560872U
};

/* Adjustment table; provided to explain the numbers in the code below. */
3692
#if 0
B
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3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707
for (i=11;i>=0;--i){ print i, " ", (1 - e(-(2^i)/65536*l(2))) * 2^(32-i), "\n"}
   11 44937.64284865548751208448
   10 45180.98734845585101160448
    9 45303.31936980687359311872
    8 45364.65110595323018870784
    7 45395.35850361789624614912
    6 45410.72259715102037508096
    5 45418.40724413220722311168
    4 45422.25021786898173001728
    3 45424.17186732298419044352
    2 45425.13273269940811464704
    1 45425.61317555035558641664
    0 45425.85339951654943850496
#endif

3708
static png_uint_32
B
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3709 3710 3711 3712 3713
png_exp(png_fixed_point x)
{
   if (x > 0 && x <= 0xfffff) /* Else overflow or zero (underflow) */
   {
      /* Obtain a 4-bit approximation */
3714
      png_uint_32 e = png_32bit_exp[(x >> 12) & 0x0f];
B
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3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755

      /* Incorporate the low 12 bits - these decrease the returned value by
       * multiplying by a number less than 1 if the bit is set.  The multiplier
       * is determined by the above table and the shift. Notice that the values
       * converge on 45426 and this is used to allow linear interpolation of the
       * low bits.
       */
      if (x & 0x800)
         e -= (((e >> 16) * 44938U) +  16U) >> 5;

      if (x & 0x400)
         e -= (((e >> 16) * 45181U) +  32U) >> 6;

      if (x & 0x200)
         e -= (((e >> 16) * 45303U) +  64U) >> 7;

      if (x & 0x100)
         e -= (((e >> 16) * 45365U) + 128U) >> 8;

      if (x & 0x080)
         e -= (((e >> 16) * 45395U) + 256U) >> 9;

      if (x & 0x040)
         e -= (((e >> 16) * 45410U) + 512U) >> 10;

      /* And handle the low 6 bits in a single block. */
      e -= (((e >> 16) * 355U * (x & 0x3fU)) + 256U) >> 9;

      /* Handle the upper bits of x. */
      e >>= x >> 16;
      return e;
   }

   /* Check for overflow */
   if (x <= 0)
      return png_32bit_exp[0];

   /* Else underflow */
   return 0;
}

3756
static png_byte
B
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3757 3758 3759 3760 3761
png_exp8bit(png_fixed_point lg2)
{
   /* Get a 32-bit value: */
   png_uint_32 x = png_exp(lg2);

3762
   /* Convert the 32-bit value to 0..255 by multiplying by 256-1. Note that the
B
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3763 3764 3765 3766
    * second, rounding, step can't overflow because of the first, subtraction,
    * step.
    */
   x -= x >> 8;
3767
   return (png_byte)(((x + 0x7fffffU) >> 24) & 0xff);
B
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3768 3769
}

3770 3771
#ifdef PNG_16BIT_SUPPORTED
static png_uint_16
B
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3772 3773 3774 3775 3776 3777 3778 3779 3780
png_exp16bit(png_fixed_point lg2)
{
   /* Get a 32-bit value: */
   png_uint_32 x = png_exp(lg2);

   /* Convert the 32-bit value to 0..65535 by multiplying by 65536-1: */
   x -= x >> 16;
   return (png_uint_16)((x + 32767U) >> 16);
}
3781
#endif /* 16BIT */
B
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3782 3783 3784 3785 3786 3787 3788 3789
#endif /* FLOATING_ARITHMETIC */

png_byte
png_gamma_8bit_correct(unsigned int value, png_fixed_point gamma_val)
{
   if (value > 0 && value < 255)
   {
#     ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814
         /* 'value' is unsigned, ANSI-C90 requires the compiler to correctly
          * convert this to a floating point value.  This includes values that
          * would overflow if 'value' were to be converted to 'int'.
          *
          * Apparently GCC, however, does an intermediate conversion to (int)
          * on some (ARM) but not all (x86) platforms, possibly because of
          * hardware FP limitations.  (E.g. if the hardware conversion always
          * assumes the integer register contains a signed value.)  This results
          * in ANSI-C undefined behavior for large values.
          *
          * Other implementations on the same machine might actually be ANSI-C90
          * conformant and therefore compile spurious extra code for the large
          * values.
          *
          * We can be reasonably sure that an unsigned to float conversion
          * won't be faster than an int to float one.  Therefore this code
          * assumes responsibility for the undefined behavior, which it knows
          * can't happen because of the check above.
          *
          * Note the argument to this routine is an (unsigned int) because, on
          * 16-bit platforms, it is assigned a value which might be out of
          * range for an (int); that would result in undefined behavior in the
          * caller if the *argument* ('value') were to be declared (int).
          */
         double r = floor(255*pow((int)/*SAFE*/value/255.,gamma_val*.00001)+.5);
B
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3815 3816 3817 3818 3819
         return (png_byte)r;
#     else
         png_int_32 lg2 = png_log8bit(value);
         png_fixed_point res;

3820
         if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0)
B
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3821 3822 3823 3824 3825 3826 3827
            return png_exp8bit(res);

         /* Overflow. */
         value = 0;
#     endif
   }

3828
   return (png_byte)(value & 0xff);
B
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3829 3830
}

3831
#ifdef PNG_16BIT_SUPPORTED
B
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3832 3833 3834 3835 3836 3837
png_uint_16
png_gamma_16bit_correct(unsigned int value, png_fixed_point gamma_val)
{
   if (value > 0 && value < 65535)
   {
#     ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3838 3839 3840 3841 3842 3843 3844
         /* The same (unsigned int)->(double) constraints apply here as above,
          * however in this case the (unsigned int) to (int) conversion can
          * overflow on an ANSI-C90 compliant system so the cast needs to ensure
          * that this is not possible.
          */
         double r = floor(65535*pow((png_int_32)value/65535.,
                     gamma_val*.00001)+.5);
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         return (png_uint_16)r;
#     else
         png_int_32 lg2 = png_log16bit(value);
         png_fixed_point res;

3850
         if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0)
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            return png_exp16bit(res);

         /* Overflow. */
         value = 0;
#     endif
   }

   return (png_uint_16)value;
}
3860
#endif /* 16BIT */
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/* This does the right thing based on the bit_depth field of the
 * png_struct, interpreting values as 8-bit or 16-bit.  While the result
 * is nominally a 16-bit value if bit depth is 8 then the result is
 * 8-bit (as are the arguments.)
 */
png_uint_16 /* PRIVATE */
3868
png_gamma_correct(png_structrp png_ptr, unsigned int value,
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    png_fixed_point gamma_val)
{
   if (png_ptr->bit_depth == 8)
      return png_gamma_8bit_correct(value, gamma_val);

3874
#ifdef PNG_16BIT_SUPPORTED
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   else
      return png_gamma_16bit_correct(value, gamma_val);
3877 3878 3879 3880
#else
      /* should not reach this */
      return 0;
#endif /* 16BIT */
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}

3883
#ifdef PNG_16BIT_SUPPORTED
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/* Internal function to build a single 16-bit table - the table consists of
 * 'num' 256 entry subtables, where 'num' is determined by 'shift' - the amount
 * to shift the input values right (or 16-number_of_signifiant_bits).
 *
 * The caller is responsible for ensuring that the table gets cleaned up on
 * png_error (i.e. if one of the mallocs below fails) - i.e. the *table argument
 * should be somewhere that will be cleaned.
 */
static void
3893
png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable,
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   PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
{
   /* Various values derived from 'shift': */
   PNG_CONST unsigned int num = 1U << (8U - shift);
3898 3899 3900 3901 3902 3903
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
   /* CSE the division and work round wacky GCC warnings (see the comments
    * in png_gamma_8bit_correct for where these come from.)
    */
   PNG_CONST double fmax = 1./(((png_int_32)1 << (16U - shift))-1);
#endif
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   PNG_CONST unsigned int max = (1U << (16U - shift))-1U;
   PNG_CONST unsigned int max_by_2 = 1U << (15U-shift);
   unsigned int i;

   png_uint_16pp table = *ptable =
3909
       (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));
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   for (i = 0; i < num; i++)
   {
      png_uint_16p sub_table = table[i] =
3914
          (png_uint_16p)png_malloc(png_ptr, 256 * (sizeof (png_uint_16)));
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      /* The 'threshold' test is repeated here because it can arise for one of
       * the 16-bit tables even if the others don't hit it.
       */
3919
      if (png_gamma_significant(gamma_val) != 0)
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      {
         /* The old code would overflow at the end and this would cause the
          * 'pow' function to return a result >1, resulting in an
          * arithmetic error.  This code follows the spec exactly; ig is
          * the recovered input sample, it always has 8-16 bits.
          *
          * We want input * 65535/max, rounded, the arithmetic fits in 32
          * bits (unsigned) so long as max <= 32767.
          */
         unsigned int j;
         for (j = 0; j < 256; j++)
         {
            png_uint_32 ig = (j << (8-shift)) + i;
#           ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
               /* Inline the 'max' scaling operation: */
3935 3936 3937 3938
               /* See png_gamma_8bit_correct for why the cast to (int) is
                * required here.
                */
               double d = floor(65535.*pow(ig*fmax, gamma_val*.00001)+.5);
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               sub_table[j] = (png_uint_16)d;
#           else
3941
               if (shift != 0)
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                  ig = (ig * 65535U + max_by_2)/max;

               sub_table[j] = png_gamma_16bit_correct(ig, gamma_val);
#           endif
         }
      }
      else
      {
         /* We must still build a table, but do it the fast way. */
         unsigned int j;

         for (j = 0; j < 256; j++)
         {
            png_uint_32 ig = (j << (8-shift)) + i;

3957
            if (shift != 0)
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               ig = (ig * 65535U + max_by_2)/max;

            sub_table[j] = (png_uint_16)ig;
         }
      }
   }
}

/* NOTE: this function expects the *inverse* of the overall gamma transformation
 * required.
 */
static void
3970
png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable,
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   PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
{
   PNG_CONST unsigned int num = 1U << (8U - shift);
   PNG_CONST unsigned int max = (1U << (16U - shift))-1U;
   unsigned int i;
   png_uint_32 last;

   png_uint_16pp table = *ptable =
3979
       (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));
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   /* 'num' is the number of tables and also the number of low bits of low
    * bits of the input 16-bit value used to select a table.  Each table is
3983
    * itself indexed by the high 8 bits of the value.
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    */
   for (i = 0; i < num; i++)
      table[i] = (png_uint_16p)png_malloc(png_ptr,
3987
          256 * (sizeof (png_uint_16)));
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   /* 'gamma_val' is set to the reciprocal of the value calculated above, so
    * pow(out,g) is an *input* value.  'last' is the last input value set.
    *
    * In the loop 'i' is used to find output values.  Since the output is
    * 8-bit there are only 256 possible values.  The tables are set up to
    * select the closest possible output value for each input by finding
    * the input value at the boundary between each pair of output values
    * and filling the table up to that boundary with the lower output
    * value.
    *
    * The boundary values are 0.5,1.5..253.5,254.5.  Since these are 9-bit
    * values the code below uses a 16-bit value in i; the values start at
    * 128.5 (for 0.5) and step by 257, for a total of 254 values (the last
    * entries are filled with 255).  Start i at 128 and fill all 'last'
    * table entries <= 'max'
    */
   last = 0;
   for (i = 0; i < 255; ++i) /* 8-bit output value */
   {
      /* Find the corresponding maximum input value */
      png_uint_16 out = (png_uint_16)(i * 257U); /* 16-bit output value */

      /* Find the boundary value in 16 bits: */
      png_uint_32 bound = png_gamma_16bit_correct(out+128U, gamma_val);

      /* Adjust (round) to (16-shift) bits: */
      bound = (bound * max + 32768U)/65535U + 1U;

      while (last < bound)
      {
         table[last & (0xffU >> shift)][last >> (8U - shift)] = out;
         last++;
      }
   }

   /* And fill in the final entries. */
   while (last < (num << 8))
   {
      table[last & (0xff >> shift)][last >> (8U - shift)] = 65535U;
      last++;
   }
}
4031
#endif /* 16BIT */
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/* Build a single 8-bit table: same as the 16-bit case but much simpler (and
 * typically much faster).  Note that libpng currently does no sBIT processing
4035
 * (apparently contrary to the spec) so a 256-entry table is always generated.
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 */
static void
4038
png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable,
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   PNG_CONST png_fixed_point gamma_val)
{
   unsigned int i;
   png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr, 256);

4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082
   if (png_gamma_significant(gamma_val) != 0)
      for (i=0; i<256; i++)
         table[i] = png_gamma_8bit_correct(i, gamma_val);

   else
      for (i=0; i<256; ++i)
         table[i] = (png_byte)(i & 0xff);
}

/* Used from png_read_destroy and below to release the memory used by the gamma
 * tables.
 */
void /* PRIVATE */
png_destroy_gamma_table(png_structrp png_ptr)
{
   png_free(png_ptr, png_ptr->gamma_table);
   png_ptr->gamma_table = NULL;

#ifdef PNG_16BIT_SUPPORTED
   if (png_ptr->gamma_16_table != NULL)
   {
      int i;
      int istop = (1 << (8 - png_ptr->gamma_shift));
      for (i = 0; i < istop; i++)
      {
         png_free(png_ptr, png_ptr->gamma_16_table[i]);
      }
   png_free(png_ptr, png_ptr->gamma_16_table);
   png_ptr->gamma_16_table = NULL;
   }
#endif /* 16BIT */

#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
   defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
   png_free(png_ptr, png_ptr->gamma_from_1);
   png_ptr->gamma_from_1 = NULL;
   png_free(png_ptr, png_ptr->gamma_to_1);
   png_ptr->gamma_to_1 = NULL;
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4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108
#ifdef PNG_16BIT_SUPPORTED
   if (png_ptr->gamma_16_from_1 != NULL)
   {
      int i;
      int istop = (1 << (8 - png_ptr->gamma_shift));
      for (i = 0; i < istop; i++)
      {
         png_free(png_ptr, png_ptr->gamma_16_from_1[i]);
      }
   png_free(png_ptr, png_ptr->gamma_16_from_1);
   png_ptr->gamma_16_from_1 = NULL;
   }
   if (png_ptr->gamma_16_to_1 != NULL)
   {
      int i;
      int istop = (1 << (8 - png_ptr->gamma_shift));
      for (i = 0; i < istop; i++)
      {
         png_free(png_ptr, png_ptr->gamma_16_to_1[i]);
      }
   png_free(png_ptr, png_ptr->gamma_16_to_1);
   png_ptr->gamma_16_to_1 = NULL;
   }
#endif /* 16BIT */
#endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
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}

/* We build the 8- or 16-bit gamma tables here.  Note that for 16-bit
 * tables, we don't make a full table if we are reducing to 8-bit in
 * the future.  Note also how the gamma_16 tables are segmented so that
 * we don't need to allocate > 64K chunks for a full 16-bit table.
 */
void /* PRIVATE */
4117
png_build_gamma_table(png_structrp png_ptr, int bit_depth)
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{
  png_debug(1, "in png_build_gamma_table");

4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132
  /* Remove any existing table; this copes with multiple calls to
   * png_read_update_info.  The warning is because building the gamma tables
   * multiple times is a performance hit - it's harmless but the ability to call
   * png_read_update_info() multiple times is new in 1.5.6 so it seems sensible
   * to warn if the app introduces such a hit.
   */
  if (png_ptr->gamma_table != NULL || png_ptr->gamma_16_table != NULL)
  {
    png_warning(png_ptr, "gamma table being rebuilt");
    png_destroy_gamma_table(png_ptr);
  }

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  if (bit_depth <= 8)
  {
     png_build_8bit_table(png_ptr, &png_ptr->gamma_table,
4136
         png_ptr->screen_gamma > 0 ?  png_reciprocal2(png_ptr->colorspace.gamma,
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         png_ptr->screen_gamma) : PNG_FP_1);

#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
   defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
4142
     if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0)
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     {
        png_build_8bit_table(png_ptr, &png_ptr->gamma_to_1,
4145
            png_reciprocal(png_ptr->colorspace.gamma));
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        png_build_8bit_table(png_ptr, &png_ptr->gamma_from_1,
            png_ptr->screen_gamma > 0 ?  png_reciprocal(png_ptr->screen_gamma) :
4149
            png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);
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     }
#endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
  }
4153
#ifdef PNG_16BIT_SUPPORTED
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  else
  {
     png_byte shift, sig_bit;

4158
     if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
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     {
        sig_bit = png_ptr->sig_bit.red;

        if (png_ptr->sig_bit.green > sig_bit)
           sig_bit = png_ptr->sig_bit.green;

        if (png_ptr->sig_bit.blue > sig_bit)
           sig_bit = png_ptr->sig_bit.blue;
     }
     else
        sig_bit = png_ptr->sig_bit.gray;

     /* 16-bit gamma code uses this equation:
      *
      *   ov = table[(iv & 0xff) >> gamma_shift][iv >> 8]
      *
      * Where 'iv' is the input color value and 'ov' is the output value -
      * pow(iv, gamma).
      *
4178
      * Thus the gamma table consists of up to 256 256-entry tables.  The table
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      * is selected by the (8-gamma_shift) most significant of the low 8 bits of
      * the color value then indexed by the upper 8 bits:
      *
      *   table[low bits][high 8 bits]
      *
      * So the table 'n' corresponds to all those 'iv' of:
      *
      *   <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1>
      *
      */
     if (sig_bit > 0 && sig_bit < 16U)
4190 4191
        /* shift == insignificant bits */
        shift = (png_byte)((16U - sig_bit) & 0xff);
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     else
        shift = 0; /* keep all 16 bits */

4196
     if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
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     {
        /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively
         * the significant bits in the *input* when the output will
         * eventually be 8 bits.  By default it is 11.
         */
        if (shift < (16U - PNG_MAX_GAMMA_8))
           shift = (16U - PNG_MAX_GAMMA_8);
     }

     if (shift > 8U)
        shift = 8U; /* Guarantees at least one table! */

     png_ptr->gamma_shift = shift;

     /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now
      * PNG_COMPOSE).  This effectively smashed the background calculation for
      * 16-bit output because the 8-bit table assumes the result will be reduced
      * to 8 bits.
      */
4216
     if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
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         png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,
4218
         png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma,
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         png_ptr->screen_gamma) : PNG_FP_1);

     else
         png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift,
4223
         png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma,
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         png_ptr->screen_gamma) : PNG_FP_1);

#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
   defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
4229
     if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0)
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     {
        png_build_16bit_table(png_ptr, &png_ptr->gamma_16_to_1, shift,
4232
            png_reciprocal(png_ptr->colorspace.gamma));
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        /* Notice that the '16 from 1' table should be full precision, however
         * the lookup on this table still uses gamma_shift, so it can't be.
         * TODO: fix this.
         */
        png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift,
            png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) :
4240
            png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);
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     }
#endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
  }
4244
#endif /* 16BIT */
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}
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#endif /* READ_GAMMA */
4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489 4490 4491 4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526 4527

/* HARDWARE OR SOFTWARE OPTION SUPPORT */
#ifdef PNG_SET_OPTION_SUPPORTED
int PNGAPI
png_set_option(png_structrp png_ptr, int option, int onoff)
{
   if (png_ptr != NULL && option >= 0 && option < PNG_OPTION_NEXT &&
      (option & 1) == 0)
   {
      int mask = 3 << option;
      int setting = (2 + (onoff != 0)) << option;
      int current = png_ptr->options;

      png_ptr->options = (png_byte)(((current & ~mask) | setting) & 0xff);

      return (current & mask) >> option;
   }

   return PNG_OPTION_INVALID;
}
#endif

/* sRGB support */
#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
   defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
/* sRGB conversion tables; these are machine generated with the code in
 * contrib/tools/makesRGB.c.  The actual sRGB transfer curve defined in the
 * specification (see the article at http://en.wikipedia.org/wiki/SRGB)
 * is used, not the gamma=1/2.2 approximation use elsewhere in libpng.
 * The sRGB to linear table is exact (to the nearest 16-bit linear fraction).
 * The inverse (linear to sRGB) table has accuracies as follows:
 *
 * For all possible (255*65535+1) input values:
 *
 *    error: -0.515566 - 0.625971, 79441 (0.475369%) of readings inexact
 *
 * For the input values corresponding to the 65536 16-bit values:
 *
 *    error: -0.513727 - 0.607759, 308 (0.469978%) of readings inexact
 *
 * In all cases the inexact readings are only off by one.
 */

#ifdef PNG_SIMPLIFIED_READ_SUPPORTED
/* The convert-to-sRGB table is only currently required for read. */
const png_uint_16 png_sRGB_table[256] =
{
   0,20,40,60,80,99,119,139,
   159,179,199,219,241,264,288,313,
   340,367,396,427,458,491,526,562,
   599,637,677,718,761,805,851,898,
   947,997,1048,1101,1156,1212,1270,1330,
   1391,1453,1517,1583,1651,1720,1790,1863,
   1937,2013,2090,2170,2250,2333,2418,2504,
   2592,2681,2773,2866,2961,3058,3157,3258,
   3360,3464,3570,3678,3788,3900,4014,4129,
   4247,4366,4488,4611,4736,4864,4993,5124,
   5257,5392,5530,5669,5810,5953,6099,6246,
   6395,6547,6700,6856,7014,7174,7335,7500,
   7666,7834,8004,8177,8352,8528,8708,8889,
   9072,9258,9445,9635,9828,10022,10219,10417,
   10619,10822,11028,11235,11446,11658,11873,12090,
   12309,12530,12754,12980,13209,13440,13673,13909,
   14146,14387,14629,14874,15122,15371,15623,15878,
   16135,16394,16656,16920,17187,17456,17727,18001,
   18277,18556,18837,19121,19407,19696,19987,20281,
   20577,20876,21177,21481,21787,22096,22407,22721,
   23038,23357,23678,24002,24329,24658,24990,25325,
   25662,26001,26344,26688,27036,27386,27739,28094,
   28452,28813,29176,29542,29911,30282,30656,31033,
   31412,31794,32179,32567,32957,33350,33745,34143,
   34544,34948,35355,35764,36176,36591,37008,37429,
   37852,38278,38706,39138,39572,40009,40449,40891,
   41337,41785,42236,42690,43147,43606,44069,44534,
   45002,45473,45947,46423,46903,47385,47871,48359,
   48850,49344,49841,50341,50844,51349,51858,52369,
   52884,53401,53921,54445,54971,55500,56032,56567,
   57105,57646,58190,58737,59287,59840,60396,60955,
   61517,62082,62650,63221,63795,64372,64952,65535
};
#endif /* SIMPLIFIED_READ */

/* The base/delta tables are required for both read and write (but currently
 * only the simplified versions.)
 */
const png_uint_16 png_sRGB_base[512] =
{
   128,1782,3383,4644,5675,6564,7357,8074,
   8732,9346,9921,10463,10977,11466,11935,12384,
   12816,13233,13634,14024,14402,14769,15125,15473,
   15812,16142,16466,16781,17090,17393,17690,17981,
   18266,18546,18822,19093,19359,19621,19879,20133,
   20383,20630,20873,21113,21349,21583,21813,22041,
   22265,22487,22707,22923,23138,23350,23559,23767,
   23972,24175,24376,24575,24772,24967,25160,25352,
   25542,25730,25916,26101,26284,26465,26645,26823,
   27000,27176,27350,27523,27695,27865,28034,28201,
   28368,28533,28697,28860,29021,29182,29341,29500,
   29657,29813,29969,30123,30276,30429,30580,30730,
   30880,31028,31176,31323,31469,31614,31758,31902,
   32045,32186,32327,32468,32607,32746,32884,33021,
   33158,33294,33429,33564,33697,33831,33963,34095,
   34226,34357,34486,34616,34744,34873,35000,35127,
   35253,35379,35504,35629,35753,35876,35999,36122,
   36244,36365,36486,36606,36726,36845,36964,37083,
   37201,37318,37435,37551,37668,37783,37898,38013,
   38127,38241,38354,38467,38580,38692,38803,38915,
   39026,39136,39246,39356,39465,39574,39682,39790,
   39898,40005,40112,40219,40325,40431,40537,40642,
   40747,40851,40955,41059,41163,41266,41369,41471,
   41573,41675,41777,41878,41979,42079,42179,42279,
   42379,42478,42577,42676,42775,42873,42971,43068,
   43165,43262,43359,43456,43552,43648,43743,43839,
   43934,44028,44123,44217,44311,44405,44499,44592,
   44685,44778,44870,44962,45054,45146,45238,45329,
   45420,45511,45601,45692,45782,45872,45961,46051,
   46140,46229,46318,46406,46494,46583,46670,46758,
   46846,46933,47020,47107,47193,47280,47366,47452,
   47538,47623,47709,47794,47879,47964,48048,48133,
   48217,48301,48385,48468,48552,48635,48718,48801,
   48884,48966,49048,49131,49213,49294,49376,49458,
   49539,49620,49701,49782,49862,49943,50023,50103,
   50183,50263,50342,50422,50501,50580,50659,50738,
   50816,50895,50973,51051,51129,51207,51285,51362,
   51439,51517,51594,51671,51747,51824,51900,51977,
   52053,52129,52205,52280,52356,52432,52507,52582,
   52657,52732,52807,52881,52956,53030,53104,53178,
   53252,53326,53400,53473,53546,53620,53693,53766,
   53839,53911,53984,54056,54129,54201,54273,54345,
   54417,54489,54560,54632,54703,54774,54845,54916,
   54987,55058,55129,55199,55269,55340,55410,55480,
   55550,55620,55689,55759,55828,55898,55967,56036,
   56105,56174,56243,56311,56380,56448,56517,56585,
   56653,56721,56789,56857,56924,56992,57059,57127,
   57194,57261,57328,57395,57462,57529,57595,57662,
   57728,57795,57861,57927,57993,58059,58125,58191,
   58256,58322,58387,58453,58518,58583,58648,58713,
   58778,58843,58908,58972,59037,59101,59165,59230,
   59294,59358,59422,59486,59549,59613,59677,59740,
   59804,59867,59930,59993,60056,60119,60182,60245,
   60308,60370,60433,60495,60558,60620,60682,60744,
   60806,60868,60930,60992,61054,61115,61177,61238,
   61300,61361,61422,61483,61544,61605,61666,61727,
   61788,61848,61909,61969,62030,62090,62150,62211,
   62271,62331,62391,62450,62510,62570,62630,62689,
   62749,62808,62867,62927,62986,63045,63104,63163,
   63222,63281,63340,63398,63457,63515,63574,63632,
   63691,63749,63807,63865,63923,63981,64039,64097,
   64155,64212,64270,64328,64385,64443,64500,64557,
   64614,64672,64729,64786,64843,64900,64956,65013,
   65070,65126,65183,65239,65296,65352,65409,65465
};

const png_byte png_sRGB_delta[512] =
{
   207,201,158,129,113,100,90,82,77,72,68,64,61,59,56,54,
   52,50,49,47,46,45,43,42,41,40,39,39,38,37,36,36,
   35,34,34,33,33,32,32,31,31,30,30,30,29,29,28,28,
   28,27,27,27,27,26,26,26,25,25,25,25,24,24,24,24,
   23,23,23,23,23,22,22,22,22,22,22,21,21,21,21,21,
   21,20,20,20,20,20,20,20,20,19,19,19,19,19,19,19,
   19,18,18,18,18,18,18,18,18,18,18,17,17,17,17,17,
   17,17,17,17,17,17,16,16,16,16,16,16,16,16,16,16,
   16,16,16,16,15,15,15,15,15,15,15,15,15,15,15,15,
   15,15,15,15,14,14,14,14,14,14,14,14,14,14,14,14,
   14,14,14,14,14,14,14,13,13,13,13,13,13,13,13,13,
   13,13,13,13,13,13,13,13,13,13,13,13,13,13,12,12,
   12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,
   12,12,12,12,12,12,12,12,12,12,12,12,11,11,11,11,
   11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,
   11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,
   11,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
   10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
   10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
   10,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
   9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
   9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
   9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
   9,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
   8,8,8,8,8,8,8,8,8,7,7,7,7,7,7,7,
   7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
   7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
   7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
};
#endif /* SIMPLIFIED READ/WRITE sRGB support */

/* SIMPLIFIED READ/WRITE SUPPORT */
#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
   defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
static int
png_image_free_function(png_voidp argument)
{
   png_imagep image = png_voidcast(png_imagep, argument);
   png_controlp cp = image->opaque;
   png_control c;

   /* Double check that we have a png_ptr - it should be impossible to get here
    * without one.
    */
   if (cp->png_ptr == NULL)
      return 0;

   /* First free any data held in the control structure. */
#  ifdef PNG_STDIO_SUPPORTED
      if (cp->owned_file != 0)
      {
         FILE *fp = png_voidcast(FILE*, cp->png_ptr->io_ptr);
         cp->owned_file = 0;

         /* Ignore errors here. */
         if (fp != NULL)
         {
            cp->png_ptr->io_ptr = NULL;
            (void)fclose(fp);
         }
      }
#  endif

   /* Copy the control structure so that the original, allocated, version can be
    * safely freed.  Notice that a png_error here stops the remainder of the
    * cleanup, but this is probably fine because that would indicate bad memory
    * problems anyway.
    */
   c = *cp;
   image->opaque = &c;
   png_free(c.png_ptr, cp);

   /* Then the structures, calling the correct API. */
   if (c.for_write != 0)
   {
#     ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
         png_destroy_write_struct(&c.png_ptr, &c.info_ptr);
#     else
         png_error(c.png_ptr, "simplified write not supported");
#     endif
   }
   else
   {
#     ifdef PNG_SIMPLIFIED_READ_SUPPORTED
         png_destroy_read_struct(&c.png_ptr, &c.info_ptr, NULL);
#     else
         png_error(c.png_ptr, "simplified read not supported");
#     endif
   }

   /* Success. */
   return 1;
}

void PNGAPI
png_image_free(png_imagep image)
{
   /* Safely call the real function, but only if doing so is safe at this point
    * (if not inside an error handling context).  Otherwise assume
    * png_safe_execute will call this API after the return.
    */
   if (image != NULL && image->opaque != NULL &&
      image->opaque->error_buf == NULL)
   {
      /* Ignore errors here: */
      (void)png_safe_execute(image, png_image_free_function, image);
      image->opaque = NULL;
   }
}

int /* PRIVATE */
png_image_error(png_imagep image, png_const_charp error_message)
{
   /* Utility to log an error. */
   png_safecat(image->message, (sizeof image->message), 0, error_message);
   image->warning_or_error |= PNG_IMAGE_ERROR;
   png_image_free(image);
   return 0;
}

#endif /* SIMPLIFIED READ/WRITE */
#endif /* READ || WRITE */