Rendered image opacity changes between zoom steps in 32 bit linear integer images
GIMP version: 2.10.6
Operating System: Windows 10 1809 64 bit
Package: Installer from gimp.org
Description of the bug
While trying to reproduce the problems from gimp#2315 (moved) I encountered a strange bug: I created an image of the size 6429x4500px and converted it to 32bit integer linear light. When zooming in and out with ctrl+mouse wheel, the "chess pattern" was visible through the 100% opacity background layer on every second zoom step and it looked like I had the layer set to ~50% opacity. Changing the layer's opacity does not do anything above 50% on those zoom levels. Only opacity settings below 50% seem to actually have an impact on how the layer is rendered.
- 9.09% zoom: 50% opacity
- 12.5% zoom: 100% opacity
- 18.2% zoom: 50% opacity
- ...
For a screencast of the problem, see https://youtu.be/zWQtINKuP5Y
Reproduction
Is the bug reproducible? Yes, always
Reproduction steps:
- Create image with 32 bit integer linear colors
- Change zoom levels via ctrl+mouse wheel or the zoom in menu entry (+)
Expected result: Rendered alpha should match with the actual alpha of the image
Actual result: Images with 100% opacity are rendered semi-transparent on every second zoom level.