pngcheck verifies the integrity of PNG, JNG and MNG files (by checking the
internal 32-bit CRCs or checksums) and optionally dumps almost all of the
chunk-level information in the image in human-readable form. For example, it
can be used to print the basic stats about an image (dimensions, bit depth,
etc.); to list the color and transparency info in its palette; or to extract
the embedded text annotations. All PNG and JNG chunks are supported, plus
almost all MNG chunks (everything but PAST, DISC, tERm, DROP, DBYK, and
ORDR). This is a command-line program with batch capabilities (e.g.,
``pngcheck *.png'').