On Mon, 14 Apr 2003 Jane25345 at aol.com wrote:
> 2. I've heard that you shouldn't compress JPEGs or other types of photos > when you are using a back-up tape drive or other back up scheme. Is it true > that compressing JPEGs and other image types will corrupt them? Not as far as I know, as long as the compression algorithm you use is 'lossless'. JPEG itself is 'lossy' [think of it in terms of lossy=loses and lossless=doesn't-lose] so if you take a JPEG, read it into photoshop, edit it, and try to save it as a JPEG again, you will slowly damage the quality of the image. I don't know of any generic compression algorithms which are lossy, it just doesn't make sense for them. However, compressing a JPEG won't save a lot of space, and with the way some compression algorithms work you may even end up with a larger file, so this is a reason not to bother compressing them when backing up. To be honest, the effort of not compressing them is usually not worth the effort. On my servers I just zip up the whole websites/ directory each week and ignore minor disk/cpu wastage. Hen | The next meeting of the Louisville Computer Society will | be April 22. The LCS Web page is <http://www.kymac.org>.
