I'm looking for "unbreakable" watermarks, so data stored in exif or image metadata are out.
I have found some interesting stuff on the web while waiting for replies here:
http://www.cosy.sbg.ac.at/~pmeerw/Watermarking/
There is a master thesis that's fairly exhaustive about algorithms and their caracteristics (what they do and how unbreakable they are). I haven't got any time to read it in depth, but this stuff looks serious. There are algorithms that support JPEG compression, cropping, gamma correction or down scaling in some way. It's C, but I can port it to Python or use C libraries from Python.
However, it's from 2001 and I guess 7 years are a long time in this field :( Does anybody have some similar and more recent stuff?
