I'm trying to figure out what would be a good approach to detecting mosaic censorship in images. You know, where you see squares of a solid color to censor a part of a photograph or something, like the face of a criminal in a newspaper.
Now, I don't want to remove the censorship, I only want to detect if it's there. But it also has to be somewhat reliable. The last thing I want is false positives. I'd rather have false negatives (i.o.w. censorship in an image which isn't detected is better than censorship being detected when there is none).
I was thinking of somehow detecting when there are small squares with evenly filled color, but that would also return positive for large (non-censored) areas filled with a color, such as a part of the sky. I guess it comes down to some sort of pattern detection, but I have no idea how to approach this...
It's ok if at first the censorship is "perfect", i.e. no JPEG-artefacts or other malformings. But I do want to compensate for that, ultimately.
Any help will be eternally appreciated :)