pnginfo is an open source utility designed for the automatic inspection of PNG images.
Example:
$ pnginfo -f lena_grey.png 
IHDR
IDAT
IDAT
IDAT
IDAT
IDAT
IDAT
IEND
$ pnginfo -f lena_grey.png -c IHDR
IHDR: width: 512
IHDR: height: 512
IHDR: bitdepth: 8
IHDR: colourtype: greyscale
IHDR: compression: deflate
IHDR: filter: adaptive
IHDR: interlace method: standard
      
      Installation
          The only dependency is BSD make (available as bmake under Linux).
          Download the code archive and extract the content.
          Then configure with ./configure, compile with make and finally install using make install.
          You can override the default paths with a file named configure.local.
        
Documentation
There is no man page yet.