Image comparison algorithm

Question

I\'m trying to compare images to each other to find out whether they are different. First I tried to make a Pearson correleation of the RGB values, which works also quite go

Answer 1

First off, correlation is a very CPU intensive rather inaccurate measure for similarity. Why not just go for the sum of the squares if differences between individual pixels?

A simple solution, if the maximum shift is limited: generate all possible shifted images and find the one that is the best match. Make sure you calculate your match variable (i.e. correllation) only over the subset of pixels that can be matched in all shifted images. Also, your maximum shift should be significantly smaller than the size of your images.

If you want to use some more advances image processing techniques I suggest you look at SIFT this is a very powerfull method that (theoretically anyway) can properly match items in images independent of translation, rotation and scale.