Soft Light mode affects alpha (painting, gradient)
Environment/Versions
- GIMP version: 2.99.14 (commit a0811ff6)
- Package: flatpak
- Operating System: Ubuntu Linux 23.04 (same issues in previous versions of GIMP, dating back some year(s)).
Description of the bug
For some reason when you use any painting tools (airbrush, paintbrush, gradient), using the "Soft Light" blend mode, it affects the alpha, turning it opaque.
However, using the Layer blend mode "soft light", with the same black-to-transparent gradient, for example, works as expected, leaving the alpha at the same value.
Reproduction
Is the bug reproducible? - Yes :)
Reproduction steps:
- Open the attached concerned_me.png
- Use the gradient tool with "FG to transparent" (black to transparent) to drag diagonally across the image from top right to bottom left.
…
Expected result: The alpha should NOT be affected by the black while painting in soft-light blending mode.
Actual result: Alpha is changed to opaque in transparent areas, as shown:
Additional information
I've talked with Pippin and a few others at Wilberfest, and have determined it's indeed a bug, and is a painting code issue.