Compare
From Notes_Wiki
<yambe:breadcrumb>Image_processing_tools|Image processing tools</yambe:breadcrumb>
compare
compare is part of ImageMagick package same as convert. It can be used to compare two images using variety of algorithms. Example usage of compare to compare two images is:
compare -metric rmse 1.jpg 2.jpg diff.jpg
Note that for this to work 1.jpg and 2.jpg should be very similar to each other. Images which are completely different or which have too many differences do not yield numeric result but intead error that images difffer too much will be returned.