The slightly modified tables reduce the number of 16-bit values that
convert to an off-by-one 8-bit value. The "makesRGB.c" code that was used
to generate the tables is now in a contrib/sRGBtables sub-directory.
the sBIT fields in the test pixel as 0, which resulted in a floating
point division by zero which was irrelevant but causes systems where
FP exceptions cause a crash. Added code to pngvalid to turn on FP
exceptions if the appropriate glibc support is there to ensure this is
tested in the future.
casts. The compression_type parameter is always assigned to, so must
be non-NULL. The cast of the profile length potentially truncated the
value unnecessarily on a 16-bit int system, so the cast of the (byte)
compression type to (int) is specified by ANSI-C anyway.
changes the 'Paeth' reconstruction function to improve the GCC code
generation on x86. The changes are only part of the suggested ones;
just the changes that definitely improve speed and remain simple.
The changes also slightly increase the clarity of the code. In a
in pngmem.c; pngvalid would attempt to call png_error() if the allocation
of a png_struct or png_info failed. This would probably have led to a
crash. The pngmem.c implementation of png_malloc() included a cast
to png_size_t which would fail on large allocations on 16-bit systems.
The logical shift fix for Microsoft Visual C is required by other compilers,
so this enables that fix for all compilers when using compile-time constants.
Under MSYS 'byte' is a name declared in a system header file, so we
changed the name of a local variable to avoid the warnings that result.
is not byte aligned, while reading. Prior to libpng-1.5.6 libpng would
overwrite the end of the image if the row width is not an exact multiple
of 8 bits and the image is not interlaced.
These fixes attend to most of the errors revealed in pngvalid, however doing
the gamma work twice results in inaccuracies that can't be easily fixed.
There is now a warning in the code if this is going to happen.
It is too risky. Exactly how png_ptr->zbuf is used is under control of the
individual chunk implementation and there could easily be significant changes
within a major release.
small percentage for 16-bit and 32-bit pixels in the typical case where the
output row buffers are appropriately aligned. The optimization was not
previously possible because the png_struct buffer was always misaligned.
caused by a bug in the code that attempted to align it; the code needs to
subtract one from the pointer to take account of the filter byte prepended to
each row.
