Non-parametric brushes are limited to 8-bit integer precision
GIMP version: 2.10.6
Operating System: Windows 10
Package: [Installer from gimp.org]
Description of the bug
In GIMP 2.10.6 when using a Paintbrush tool, parametric brush, in Default layer mode and Default brush mode, with standard values as below:
[EDIT: Force should be 50 by default]
reduced quality of the brush can be noticed. This is best viewed when using a white on black background (same layer or separate), or whenever white is interacting with black surface (the same layer).
The edge of the brush is more 'indexed' and less smooth, and the whites seem more aggresive in volume. Comparing to the same brush when in Legacy brush mode, we can notice a distinction in quality:
This happens in all Image Precision mods. When changing the Composite space of the Default layer to RGB (perceptual), the whites become smoother only if they are on separate, transparent layer and not interacting with other, darker colors. To avoid this 'posterization' of the brush, it can only be achieved by changing the Default brush to Legacy brush mode. It's harder to notice these issues when using the same brush and painting with black color, it's smooth and more seamless.
Is the bug reproducible? [Always]
- Create a new file (preferably with Precision above 8-bit integer)
- Fill out the background layer with black.
- Create a new Default transparent layer above it.
- Select the Paintbrush tool (Default brush mode), one of the parametric brushes (for example "Hardness 050" with standard, default values), use the white color, and test out the brush on the transparent layer.
- Shift to different brush modes (Default to Legacy) to notice the difference in quality.
Expected result: Smooth, seamless brush strokes.
Actual result: Harder brush with indexed edges.
Same subject was further discussed, with additional examples and files on the issue, and ideas of what might be the cause for the behaviour, in the link bellow: