Hello again everyone, I think I have a GIF which libnsgif does not handle correctly:
https://github.com/libvips/libvips/blob/master/test/test-suite/images/dispose-previous.gif This GIF has three frames which draw three concentric red circles. The GIF does this: - clear frame frame 0: - disposal_method COMBINE - draw outermost red circle frame 1: - disposal_method RESTORE - draw middle red circle frame 2: - disposal_method RESTORE - draw inner red circle So the viewer should see this: https://github.com/libvips/libvips/blob/master/test/test-suite/images/dispose-previous.png frame 0: - outer circle frame 1: - outer + middle frame 2: - outer + inner However, if you view with libnsgif, you'll see frame 2 has all three circles, ie. the middle frame is not removed. Looking at the code, the problem seems to be that gif_internal_decode_frame() calls gif__record_previous_frame() before it calls gif__recover_previous_frame(). This means that if you have two frames with RESTORE dispose in a row, the second restore will be missed, since it will save the frame (overwriting the restore) before it tries to restore it. The simplest fix is probably to simply move the record handler to just after the recover. I think this makes intuitive sense -- you want to finish disposing of the previous frame before you record the current state. John _______________________________________________ netsurf-dev mailing list -- netsurf-dev@netsurf-browser.org To unsubscribe send an email to netsurf-dev-le...@netsurf-browser.org
