chunk length written by libpng-1.6.0 and 1.6.1.

    (Flavio Medeiros).

png_set of the transform function, but that doesn't matter unless the
transform function changes the rowbuf size, and that is only valid if
transform_info is called.

warning would be produced if the end of the deflate stream wasn't read
in the last row.  The warning is harmless.

handling.

technically valid, although a reasonable treatment of division would
show it to be incorrect.

    library (Claudio Bley):
  Introduced a PNG_LIB_TARGETS variable that lists all activated library
    targets.  It is an error if this variable ends up empty, ie. you have
    to build at least one library variant.
  Made the *_COPY targets only depend on library targets actually being build.
  Use PNG_LIB_TARGETS to unify a code path.
  Changed the CREATE_SYMLINK macro to expact the full path to a file as the
    first argument. When symlinking the filename component of that path is
    determined and used as the link target.
  Use copy_if_different in the CREATE_SYMLINK macro.

a flag to change default. In 1.6.0 when the simplified API was used
to produce color-mapped output from an input image with no gamma
information the gamma assumed for the input could be different from
that assumed for non-color-mapped output.  In particular 16-bit depth
input files were assumed to be sRGB encoded, whereas in the 'direct'
case they were assumed to have linear data.  This was an error.  The
fix makes the simplified API treat all input files the same way and
adds a new flag to the png_image::flags member to allow the
application/user to specify that 16-bit files contain sRGB data
rather than the default linear.
Fixed bugs in the pngpixel and makepng test programs.

    prefixing This adds an API to set optimization options externally,
    providing an alternative and general solution for the non-portable
    run-time tests used by the ARM Neon code.  It also makes those tests
    compile and link on Android.
  The order of settings vs options in pnglibconf.h is reversed to allow
    settings to depend on options and options can now set (or override) the
    defaults for settings.

an unhandled chunk.

handle chunks even when they have been tagged PNG_HANDLE_CHUNK_NEVER.

trouble with CRLF line endings.