[NickC_dev]

There's a publicly available implementation of a perceptual hashing algorithm called phash at http://phash.org. I use some of their c++ code to detect reposts on an image sharing site I run (http://lolstack.com).

[pavel_lishin]

Could you add RSS?

[NickC_dev]

It's definitely on my summer to-do list. You're the first person to ask.