Quote:
Originally Posted by Tickler
1. You can do color shifting to hide numbers, in an image. Pick some square areas, and bump the colors in that area a bit. Basically be almost invisable to the naked eye.
For a "0" = current color + 4*10
For a "1" = current color + 4*1
For a "2" = current color + 4*2
For a "3" = current color + 4*3
...
For a "8" = current color + 4*8
For a "9" = current color + 4*9
Then just do a "mask" comparison between the original and the encoded to reverse the calculation.
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This is fine for transmitting hidden data between receiving parties, but I think it has its limitations, especially in video, for trying to track a file. Simply because any type of compression algorithm will result in the hidden message being lost, so transcoding a video from say mpeg to flv will kill the information. I would say inserting random frames is far better since they will survive transcoding and nobody is going to search 1000s of frames for 1-10 "randomly" injected tracking frames.
Random because to the end user it's random, the to producer they could inject constantly eg every (#frames / 10 + 15) frames - random to the end user, the producer knows exactly where to look each time though.