libpng-1.6.12 is available from
ftp://ftp.simplesystems.org/pub/png/src/libpng16
and from
http://libpng.sf.net

Changes since the last public release (1.6.11):
  Relocated new code from 1.6.11 in png.c to a point after the
    declarations (Max Stepin).
  Changed file permissions of contrib/tools/intgamma.sh,
    test-driver, and compile from 0644 to 0755 (Cosmin).
  Ensure "__has_attribute()" macro exists before trying to use it with
    old clang compilers (MacPorts Ticket #43939).

Glenn