Ask HN: Free software to compare images, similar to Googles reverse image search?

Try libpuzzle : http://www.pureftpd.org/project/libpuzzle

I'm using it in an erlang wrapper (https://github.com/eraserewind/erlpuzzle) to crawl tumblr & reddit images, and then dedupe it.

Puzzle signatures are easy to index. I'm using ElasticSearch

I would like to store images in two separate locations and make sure there is no overlap. Ideally, this would extend to images that were the same but different sizes, etc but not extremely pressing.

One of the images stores will come from scraping and I would like to compare it to see if the same image already exists on my server.