Duplicate image detection algorithms?

Question

I am thinking about creating a database system for images where they are stored with compact signatures and then matched against a \"query image\" that could be a resized, c

Answer 1

SURF should do its job.

http://en.wikipedia.org/wiki/SURF

It is fast an robust, it is invariant on rotations and scaling and also on blure and contrast/lightning (but not so strongly).
There is example of automatic panorama stitching.

Check article on SIFT first
http://en.wikipedia.org/wiki/Scale-invariant_feature_transform