TinEye tries to do that and the best part is that it mostly succeeds. The new image search engine, powered by Idée's technology and currently in private beta, has an index of 487 million images (Google's index is at least 12 times bigger) and manages to find identical versions of an image or alterations. "TinEye frequently returns image results with colour adjustments, added or removed text, crops, and slight rotations. TinEye can also detect images that are part of a collage or have been blended with another image."
How does it work then? "TinEye uses sophisticated pattern recognition algorithms to find your image on the web without the use of metadata or watermarks. TinEye instantly analyzes your query image to create a compact digital signature or 'fingerprint' for it. TinEye searches for your image on the web by comparing its fingerprint to the fingerprint of every single other image in the TinEye search index."