Alpha channel reverts to canvas at high zoom
Environment/Versions
- GIMP version: 2.10.32 and 2.99.10
- Package: gimp.org installer
- Operating System: Windows 10
Description of the bug
At a high level of zoom, the transparent area of the image switches to the canvas colour, rather than the grey checkerboard. The screenshots below show a simple recreation of the issue. I have created a transparent region within a 1920 x 1080px image. We zoom in the highlighted area without issue to 4789% without issue, but at 4790% the transparent region is replaced with the canvas colour.
Some additional information:
- I can confirm that it is indeed the canvas colour showing, as I've tried changing it while zoomed in.
- The zoom value at which this issue occurs is not fixed. On a very large image of 25986 x 18797px, the point at which the issue occurs is 240% -> 241%.
- In contrast, on a very small file eg. 100 x 100px, I wasn't able to recreate the issue as the max zoom value of 25600% is reached before it occurs.
Reproduction
Is the bug reproducible? Always
Reproduction steps:
- Create new image (recommend 1000 x 1000px, though I was able to reproduce at 200 x 200px)
- Add alpha channel
- Use eraser or selection/delete to create transparent area
- Continue zooming into area
…
Expected result: The transparent area remains transparent.
Actual result: The transparent area shows the canvas colour.