On Sep 19, 2010, at 11:50 AM, tedd wrote: > At 12:36 AM +0100 9/18/10, Ashley Sheridan wrote: >> >> I know this is getting a little off-topic here, but surely the way a >> jpeg destroys data in an image would destroy the stenography information >> too? To the human eye all would appear normal, but the copyright info >> would be lost? >> >> I don't know much about this sort of thing, so I'm making assumptions >> here. > > > It's the difference between lossless and lossy compression. The first meaning no loss in data and the second is loss of data. PNG and jpeg is lossless whereas gif is lossy. Actually GIF is lossless (it uses LZW encoding) PNG is also lossless (Ii uses DEFLATE). The specification for JPEG supports both lossy and lossless. And then, of course there is wavelet used in JPEG2000 and other wavelets These are lossy. Tom -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
