Image comparison module for PHP

Is there any basic (free or not), but usable - not like li开发者_C百科bpuzzle - image fingerprinting/similarity/compare module for PHP, which works akin to TinEye or Google image upload search? It's basically needed to avoid uploading almost the same (but with watermarks, resized etc.) image twice into a set of 50-300 images.

Take a look at http://www.intelliot.com/2008/03/sorted-directory-listing-image-resizing-comparison-and-similarity-in-php/

This is a very interesting educational article about image comparison. It wouldn't be hard at all to adapt to PHP using the GD library or ImageMagick.

http://www.hackerfactor.com/blog/index.php?/archives/432-Looks-Like-It.html

Good luck !