png_memset(), png_memcpy(), and png_memcmp() macros.

support.  Now "make check" will succeed even if libpng is compiled with
-DPNG_NO_READ or -DPNG_NO_WRITE.  The tests performed are reduced, but the
basic reading and writing of a PNG file is always tested by one or more of
the tests.

except in pngtest.c and example.c where these macros are not visible.

errors) and cause it not to fail at the comparison step if libpng lacks support
for writing chunks that it reads from the input (currently only implemented
for compressed text chunks).

This is a small function, but avoiding compiling it also avoids needing
to link with "-lm" unnecessarily.

builds.  Restored png_get_channels() to WRITE-only builds.

issues with 1.12 and insisting on anything less would allow 1.12 to be used.

patch; they are needed by png_set_IHDR() for both read and write.  Fix
some ifdefs that caused the contrib/pngminim/ applications to not compile.

on read and write.  In libpng 1.6 the two cases can be distinguished and
considerable code cleanup, and extra error checking, is possible.  This
makes calls on the write side that have no effect be ignored with a
png_app_error(), which can be disabled in the app using
png_set_benign_errors(), and removes the spurious use of usr_channels
on the read side.

a consistent style for (sizeof type) and (sizeof (array))

of strcpy() was accidentally re-introduced in libpng16; this change replaces
it with strncpy().

Because of the changes to support symbol prefixing PNG_INTERNAL_FUNCTION
declares floating point APIs during libpng builds even if they are completely
disabled. This requires the png floating point types (png_double*) to be
declared even though the functions are never actually defined.  This
change provides a dummy definition so that the declarations work, yet any
implementation will fail to compile because of an incomplete type.

comments.  It has apparently been wrong since libpng-1.0.1c (confusing
use of a 1D and a 2D array for the image source).

They have not been exported to applications since libpng12.

(This is probably unnecessary because it's inside a __GNUC__ block.)

This has been missing since the feature was introduced in libpng-1.6.0beta04.

distributions; it depends on configure, which is not included in those
archives.

ignore all unknown chunks and all known chunks except for IHDR, PLTE, tRNS,
IDAT, and IEND.  Previously it only meant ignore all unknown chunks, the
same as num_chunks == 0. Revised png_image_skip_unused_chunks() to
provide a list of chunks to be processed instead of a list of chunks to
ignore.  Revised contrib/gregbook/readpng2.c accordingly.

replacement with png_convert_to_rfc1123_buffer().

MNG files).

(only update the value when it actually increases, move test for whether
the check is wanted out of the function.

generating the linker mapfile symbol prefix.

The compiler performs an optimization which is safe; however it then warns
about it.  Changing the type of 'palette_number' in pngvalid.c removes the
warning.