How to detect if a PNG was edited with PhotoShop? [closed]

Question

I have a directory of screen shots of some software in PNG format. I found that one was edited in PhotoShop, or a similar tool. I would like to identify additional PNGs in the directory that were also edited. If the editor were careless, is there any batch tool that could be used to see if the files were opened and saved from PhotoShop, e.g. by looking at the metadata or other details?

Answer 1

A heuristic (purely empirical, this is not documented by Adobe, hence it can change from version to version) is to look for a iCCP chunk with the name 'Photoshop ICC profile'.

A quick and dirty oneliner (linux or mingw):

$ head -c 256 file.png  | perl -e '$/=undef; print ((<> =~ /iCCPPhotoshop/)?
 "photoshop"  : "normal");'

Worked for me, but it's obviously not infalible. The head -c 256 takes into account that the chunk will be before the pixels data (and the palette if present), so as not to grep the entire image.

Bear also in mind that if the image was edited in Photoshop and afterwards edited by other editor or processor, the iCCP will probably not survive.

If you want to peek inside the PNG structure, there is this neat tool for Windows: http://entropymine.com/jason/tweakpng/

Answer 2

There is a website called image edited that is a quick and easy process.