Duplicate images

I've been using Dup Detector to find duplicate image files (damn you 4chan). I've just found out that it doesn't detect .gif files though.
Are there any programs that work the same as Dup Detector, but can support gifs?

>>8
I can understand what you're saying about hash checking. That would detect duplicate files regardless of filetype.

However, say you have a BMP and a PNG which are the same image, just in different formats. Or two JPEGs which are from the same source image but use different levels of compression. In both cases, their hashes would not match. So you'd need a program which could look at the color data and compare them to see how similar they look.

I've never used any sort of file comparison program (except diff) but I'm guessing that's what the OP wants.