PNG Check 2.3.0 is available for download:
http://hobbes.nmsu.edu/h-search.php?key=pngcheck
"PNG Check, a command-line program to check and report information or subimages from PNG/MNG image/animation files. Binaries and source code are included. Open source under the GNU GPL V2 license."
By Mentore Siesto.
Source: eCSoft/2