[libpng16] Made default Zlib compression settings be configurable. This adds #defines to

pnglibconf.h to control the defaults.

ANNOUNCE

 
-Libpng 1.6.0beta35 - December 19, 2012
+Libpng 1.6.0beta35 - December 21, 2012
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -569,7 +569,9 @@ Version 1.6.0beta34 [December 19, 2012]
   Disassembled the version number in scripts/options.awk (necessary for
     building on SunOs).
 
-Version 1.6.0beta35 [December 19, 2012]
+Version 1.6.0beta35 [December 21, 2012]
+  Made default Zlib compression settings be configurable. This adds #defines to
+    pnglibconf.h to control the defaults.
 
   ===========================================================================
                        NOTICE November 17, 2012:

CHANGES

@@ -4321,7 +4321,9 @@ Version 1.6.0beta34 [December 19, 2012]
   Disassembled the version number in scripts/options.awk (necessary for
     building on SunOs).
 
-Version 1.6.0beta35 [December 19, 2012]
+Version 1.6.0beta35 [December 21, 2012]
+  Made default Zlib compression settings be configurable. This adds #defines to
+    pnglibconf.h to control the defaults.
 
   ===========================================================================
                        NOTICE November 17, 2012:

pngwrite.c

@@ -501,15 +501,19 @@ png_create_write_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
     */
    png_ptr->zbuffer_size = PNG_ZBUF_SIZE;
 
-   png_ptr->zlib_strategy = Z_FILTERED; /* may be overridden if no filters */
-   png_ptr->zlib_level = Z_DEFAULT_COMPRESSION;
+   /* The 'zlib_strategy' setting is irrelevant because png_default_claim in
+    * pngwutil.c defaults it according to whether or not filters will be used,
+    * and ignores this setting.
+    */
+   png_ptr->zlib_strategy = PNG_Z_DEFAULT_STRATEGY;
+   png_ptr->zlib_level = PNG_Z_DEFAULT_COMPRESSION;
    png_ptr->zlib_mem_level = 8;
    png_ptr->zlib_window_bits = 15;
    png_ptr->zlib_method = 8;
 
 #ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
-   png_ptr->zlib_text_strategy = Z_DEFAULT_STRATEGY;
-   png_ptr->zlib_text_level = Z_DEFAULT_COMPRESSION;
+   png_ptr->zlib_text_strategy = PNG_TEXT_Z_DEFAULT_STRATEGY;
+   png_ptr->zlib_text_level = PNG_TEXT_Z_DEFAULT_COMPRESSION;
    png_ptr->zlib_text_mem_level = 8;
    png_ptr->zlib_text_window_bits = 15;
    png_ptr->zlib_text_method = 8;

pngwutil.c

@@ -338,10 +338,10 @@ png_deflate_claim(png_structrp png_ptr, png_uint_32 owner,
             strategy = png_ptr->zlib_strategy;
 
          else if (png_ptr->do_filter != PNG_FILTER_NONE)
-            strategy = Z_FILTERED;
+            strategy = PNG_Z_DEFAULT_STRATEGY;
 
          else
-            strategy = Z_DEFAULT_STRATEGY;
+            strategy = PNG_Z_DEFAULT_NOFILTER_STRATEGY;
       }
 
       else

scripts/pnglibconf.dfa

@@ -182,6 +182,22 @@ setting PREFIX
 
 setting DEFAULT_READ_MACROS default 1
 
+# These settings configure the default compression level (0-9) and 'strategy';
+# strategy is as defined by the implementors of zlib, it describes the input
+# data and modifies the zlib parameters in an attempt to optimize the balance
+# between search and huffman encoding in the zlib algorithms.  The defaults are
+# the zlib.h defaults - the apparently recursive definition does not arise
+# because the name of the setting is prefixed by PNG_
+#
+# The TEXT values are the defaults when writing compressed text (all forms)
+
+setting Z_DEFAULT_COMPRESSION default Z_DEFAULT_COMPRESSION
+setting Z_DEFAULT_STRATEGY default Z_FILTERED
+setting Z_DEFAULT_NOFILTER_STRATEGY default Z_DEFAULT_STRATEGY
+
+setting TEXT_Z_DEFAULT_COMPRESSION default Z_DEFAULT_COMPRESSION
+setting TEXT_Z_DEFAULT_STRATEGY default Z_DEFAULT_STRATEGY
+
 # The alternative is to call functions to read PNG values, if
 # the functions are turned *off* the read macros must always
 # be enabled, so turning this off will actually force the

scripts/pnglibconf.h.prebuilt

@@ -3,7 +3,7 @@
 
 /* pnglibconf.h - library build configuration */
 
-/* Libpng 1.6.0beta35 - December 19, 2012 */
+/* Libpng 1.6.0beta35 - December 21, 2012 */
 
 /* Copyright (c) 1998-2012 Glenn Randers-Pehrson */
 
@@ -34,8 +34,13 @@
 #define PNG_QUANTIZE_RED_BITS 5
 #define PNG_sCAL_PRECISION 5
 #define PNG_sRGB_PROFILE_CHECKS 2
+#define PNG_TEXT_Z_DEFAULT_COMPRESSION Z_DEFAULT_COMPRESSION
+#define PNG_TEXT_Z_DEFAULT_STRATEGY Z_DEFAULT_STRATEGY
 #define PNG_WEIGHT_SHIFT 8
 #define PNG_ZBUF_SIZE 8192
+#define PNG_Z_DEFAULT_COMPRESSION Z_DEFAULT_COMPRESSION
+#define PNG_Z_DEFAULT_NOFILTER_STRATEGY Z_DEFAULT_STRATEGY
+#define PNG_Z_DEFAULT_STRATEGY Z_FILTERED
 /* end of settings */
 /* options */
 #define PNG_16BIT_SUPPORTED