On Tue, Aug 14, 2007 at 04:55:56PM +0100, Emanuele D'Arrigo wrote:
Actual per-pixel subtraction gives interesting-looking results if the difference is large enough, but they can be sometimes difficult to relate to the original images and subtle changes will be difficult to spot due to their low contrast. Also, given a 0 to 255 range in value for each pixel, the result of a subtraction operation would be in the range -255 to +255. This then needs to be compressed back into a displayable 0 to 255 which effectively loses half of the information.
What about that new thing that guy showed off last week on a slashdot piece with the modified JPEGs of Al Q'aeda? Is that pertinent here?
Cheers, -- jra