Addendum: The amazing thing about Get Curves isn't just getting the curves from your photo editing, but that it can be used to opensource and share pretty much any colour processing filter that people charge hundreds of dollars for. At the site I linked to, there's a sample of curves made from the Alien Skin Photoshop plugin. The results should be more or less identical to the "real" thing.
Resynthesizer will do an extremely complex calculation of what should/might be there, and create textures based on the surrounding area. I think. If you're interested, the original work was based on a extremely elaborate phd dissertation that's available online. The whole thing is way over my head, but it works.