drawoc wrote: > If you simply open a jpeg, and then save it as a jpeg without > modification, you will lose data. Jpeg is always lossy. More > compression artifacts will be introduced in the saved image. There is > no sane way to avoid this behavior. Technically that's true (but see below), but have you actually seen this ? Given a certain moderate compression ratio, how many open/slight edit/save cycles does it take before you can visually notice that the quality is worse than what you started with ? 2 ? 5 ? 10 ? > If you allow the user to save back to jpeg, then you will not "honour > the quality/file size trade-off" because the user will be slowly > destroying their image every time they save and re-open. It turns out that (typically) open/save of a jpeg does not cause a steady decrease in quality, instead it asymptotes to a steady state. That's because once DCT coefficients have been quantised, they tend to get re-quantised to the same values. There is no question that a lossily compressed format is not what you want to use to create original artwork or do high quality editing or re-purposing, but I think I can be confident that the vast majority of image use is casual and non critical and in the jpeg format - all those billions of digital photo's taken every day by ordinary people. > We're not saying that you can't slowly destroy your image - you still > have the freedom to do that. We just want you to click a single button > that says, "yes, I want to destroy my image", if you really do like > destroying images. But you're saving to a lossy compressed file format - by doing that you have made that choice. Having a nag telling you all the time that "you do realise that jpeg is lossy, don't you?" seems fairly pointless. Graeme Gill. _______________________________________________ gimp-developer-list mailing list gimp-developer-list@xxxxxxxxx https://mail.gnome.org/mailman/listinfo/gimp-developer-list
