GNOME Bugzilla – Bug 339370
Optimized animated GIF preview in open is screwy
Last modified: 2008-01-15 13:07:07 UTC
Please describe the problem: When clicking on an optimized animated GIF in the open dialog for a preview the preview shown is messed up. Steps to reproduce: 1. Optimize an animated GIF in which the last frames have a few changes. 2. Save this animated GIF 3. Open it and look at the preview Actual results: The layers from previous frames are added together in the preview. Expected results: The preview seems to be that of the very last frame of an animation. The preview shown should match the last frame as shown as if I just opened the image. Does this happen every time? It depends on the design of the optimized animated GIF. If the last frames had big changes rather than a few pixels changing, the effect isn't noticed. Other information: http://www.ulillillia.us/images/thefallglide.gif Try previewing the effect with this animation where the effect is quite intense. You should have an effect as shown in this screenshot: http://www.ulillillia.us/temporary/animatedGIFpreviewbug.png I get something similar with many of my other animations. This is just one of the worst ones in the preview.
Please attach a small example animation to this report.
Created attachment 64087 [details] Sample animation This is the same animation I posted a link to. It's a 26 KB file which seems kind of big (my biggest is over ten times that, but this is sufficient enough). I created the attachment as you asked me to.
This is due to the preview code not doing the alpha channel binarization for indexed images that the projection is doing. Since the thumbnail is created from the image preview and not from the projection, you are seeing these artefacts.
Perhaps the gifload plug-in should implement thumbnail loading functionality. It knows that the file is an animation and could deliver a correct preview of the first frame.
This doesn't completely fix the problem described here but since it's an improvement and cuts down the time to load a preview, I've done this change in CVS: 2006-04-24 Sven Neumann <sven@gimp.org> * plug-ins/common/gifload.c: implement a thumbnail load procedure that loads only the first frame of a GIF animation. The remaining issue is pretty well handled by bug #25272 so lets close this as a duplicate. *** This bug has been marked as a duplicate of 25272 ***