|LibPNG supports almost all PNG features, is extensible, and has been extensively tested for|
over 20 years. The home site for development versions (i.e., may be buggy or subject
to change or include experimental features) is http://libpng.sourceforge.net/, and
the place to go for questions about the library is the png-mng-implement mailing list.
hg clone https://toolshed.g2.bx.psu.edu/repos/devteam/package_libpng_1_6_7