Description
Bug report
Describe the bug
Treating animated images as a very tall image causes "bleed-through" between the top and bottom of the frames when upscaling.
To Reproduce
Input (sorry for how irritating it is):
vipsthumbnail 'banana.gif[n=-1]' -s 128x128 -o output.gif
The bottoms of the feet have bled onto the top of the frames below them, leading to thin moving black lines at the top of the image.
(this difference isn't going to be visible in the Github UI if you're using the dark theme)
Expected behavior
The output of each scaled frame should be independent of the pixels on the adjacent frames.
Environment
(please complete the following information)
- OS: Ubuntu 22.04
- Vips: 8.15.2