I'm bored at work and ran across a CD that is packaged in a cardboard cover. The previous owner spilled something funky and brown all over it. The end result is actually kind of cool.....kinda like someone added a texture layer in Photoshop....LOL. Now I'm wondering if there is a way to reverse engineer this and isolate just the spill. I'm thinking I could use Google image search to locate the original unsullied photo and shoot the soiled one. Is there anysort of filter to overlap the layers and subtract that which is the same on each layer and just show "the difference"? Or am I dreaming of something that does not exist. It's nothing serious, but was just wondering if there was a way to do it. I could then save this "spill" as a layer and use it on any photo I wanted to do.......in a way immortalizing the inactions of the previous owner to clean up his spill quickly. Any thoughts?