content-based image retrieval?

Hello,
I have the feeling this is a FAQ, but I can't find an answer to it anywhere in the Postgres documentation, website, or google.

Is there anything out there for PostgreSQL for doing content-based image retrieval? e.g. "select all images that look like this one/are the same colors as this one"?

Google returns a few references to something called Chabot, Virage, and a few other ancient sites, but there's very little meat on anything that even still exists.

There's a possibility I'll be building such a system, and currently I'm kind of being leaned towards Oracle and it's interMedia stuff. I'd like to stick with PostgreSQL if possible.

I'm not a rocket scientist, so I am not under the impression I can build my own CBIR. I'd like to know if there's anything that actually exists and works that works with PostgreSQL.

Thanks!