How to compare 2 images from command line

[Wojciech Puchar]

> I'm trying to determine if 2 jpeg images are identical. The images are 
> screenshots taken with scrot at different times. The point is to know if the 
> display is working correctly. I tried to use 'diff' but without success, 
> probably because of the metadata included in the image. I also tried the

cmp does byte-to byte comparision.

if you want to make sure uncompressed bitmaps are the same then uncompress 
(cmp) and then compare