This can be uber useful for a lot of stuff. We developed something functionally very similar to detect image spam at my $employer a couple of years ago. Good stuff.

It's also GPL so if you base your application on it it'll have to have a very liberal license too.

You'll have to use the restrictive GPL-3 or compatible licenses and be forbidden from using the more liberal licenses. All point of view.

(I wish software library people would put their licenses up front instead of making me download it to find them.)

It says 'pHash is an open source software library released under the GPLv3 license that implements several perceptual hashing algorithms, and provides a C++ API to use those functions in your own programs.' right on the frontpage, looks pretty clear to me

I'll be darned. It even has GPL3 highlighted and I missed it. I'll have to change me wish to a more personal one.

It's not AGPL, though, so IIRC you can use it in any web apps you come up with without having to publish source.

No updates for a year. Abandoned?

A year? 0.3 came out in Nov 08.

pHash 0.3

11.03.2008

OK OK, not quite a year yet ..

Keep in mind, the authors are using the American date system. That's November 3, 2008, not March 11th.

Ah yes, the US-only "middle endian" theory of date notation. Wonderful. Not confusing at all. OK, November, I stand corrected.