Fast and simple image hashing algorithm

Question

I need a (preferably simple and fast) image hashing algorithm. The hash value is used in a lookup table, not for cryptography.

Some of the images are \"computer grap

Answer 1

Have a look at this tutorial on the phash algorithm http://www.hackerfactor.com/blog/index.php?/archives/432-Looks-Like-It.html which is used to find closely matching images.