libpng-1.6.7 is available from
ftp://ftp.simplesystems.org/pub/png/src/libpng16
and from
http://libpng.sf.net/

Changes since the last public release (1.6.6):

  Revised unknown chunk code to correct several bugs in the NO_SAVE_/NO_WRITE
    combination
  Allow HANDLE_AS_UNKNOWN to work when other options are configured off. Also
    fixed the pngminim makefiles to work when $(MAKEFLAGS) contains stuff
    which terminates the make options (as by default in recent versions of
    Gentoo).
  Avoid up-cast warnings in pngvalid.c. On ARM the alignment requirements of
    png_modifier are greater than that of png_store and as a consequence
    compilation of pngvalid.c results in a warning about increased alignment
    requirements because of the bare cast to (png_modifier*). The code is safe,
    because the pointer is known to point to a stack allocated png_modifier,
    but this change avoids the warning.
  Fixed default behavior of ARM_NEON_API. If the ARM NEON API option was
    compiled without the CHECK option it defaulted to on, not off.
  Check user callback behavior in pngunknown.c. Previous versions compiled
    if SAVE_UNKNOWN was not available but did nothing since the callback
    was never implemented.
  Merged pngunknown.c with 1.7 version and back ported 1.7 improvements/fixes
  Made changes for compatibility with automake 1.14:
    1) Added the 'compile' program to the list of programs that must be cleaned
       in autogen.sh
    2) Added 'subdir-objects' which causes .c files in sub-directories to be
       compiled such that the corresponding .o files are also in the
       sub-directory.  This is because automake 1.14 warns that the
       current behavior of compiling to the top level directory may be removed
       in the future.
    3) Updated dependencies on pnglibconf.h to match the new .o locations and
       added all the files in contrib/libtests and contrib/tools that depend
       on pnglibconf.h
    4) Added 'BUILD_SOURCES = pnglibconf.h'; this is the automake recommended
       way of handling the dependencies of sources that are machine generated;
       unfortunately it only works if the user does 'make all' or 'make check',
       so the dependencies (3) are still required.
  Cleaned up (char*) casts of zlib messages. The latest version of the Intel C
    compiler complains about casting a string literal as (char*), so copied the
    treatment of z_const from the library code into pngfix.c
  Simplified error message code in pngunknown. The simplification has the
    useful side effect of avoiding a bogus warning generated by the latest
    version of the Intel C compiler (it objects to
    condition ? string-literal : string-literal).
  Make autogen.sh work with automake 1.13 as well as 1.14. Do this by always
    removing the 1.14 'compile' script but never checking for it.
  Added ARMv8 support (James Yu <james.yu at linaro.org>).  Added file
    arm/filter_neon_intrinsics.c; enable with -mfpu=neon.
  Revised pngvalid to generate size images with as many filters as it can
    manage, limited by the number of rows.
  Cleaned up ARM NEON compilation handling. The tests are now in pngpriv.h
    and detect the broken GCC compilers.
  Allow clang derived from older GCC versions to use ARM intrinsics. This
    causes all clang builds that use -mfpu=neon to use the intrinsics code,
    not the assembler code.  This has only been tested on iOS 7. It may be
    necessary to exclude some earlier clang versions but this seems unlikely.
  Changed NEON implementation selection mechanism. This allows assembler
    or intrinsics to be turned on at compile time during the build by defining
    PNG_ARM_NEON_IMPLEMENTATION to the correct value (2 or 1).  This macro
    is undefined by default and the build type is selected in pngpriv.h.
  Fixed #include in filter_neon_intrinsics.c and ctype macros. The ctype char
    checking macros take an unsigned char argument, not a signed char.

Glenn