Bug 434263

Summary: Color dodge brush mask produces black textures around strokes with certain settings
Product: [Applications] krita Reporter: tomtomtomreportingin
Component: Brush enginesAssignee: Krita Bugs <krita-bugs-null>
Status: RESOLVED FIXED    
Severity: normal Keywords: regression
Priority: NOR    
Version First Reported In: 4.4.3-beta1   
Target Milestone: ---   
Platform: Appimage   
OS: Linux   
Latest Commit: https://invent.kde.org/graphics/krita/commit/c40b4ca469da442d110e72cce307179039a276d0 Version Fixed/Implemented In:
Sentry Crash Report:

Description tomtomtomreportingin 2021-03-11 00:17:32 UTC 
SUMMARY
Regression introduced in 4.2: When the color dodge brush mask is large and the mask's opacity and flow options are turned off, strokes will have 100% black texture edges.

STEPS TO REPRODUCE
1. Select Basic 2 Opacity Brush.
2. Enable Masked Brush Tip.
3. Change Mask blending mode to Color Dodge.
4. Set Mask diameter to 200.
5. Turn off Mask's opacity and flow options.
6. Draw with a non-black color and observe.

OBSERVED RESULT
Black textures around the stroke.

EXPECTED RESULT
No black textures around the stroke.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Debian sid
KDE Plasma Version: 5.20.5
KDE Frameworks Version: 5.78.0
Qt Version: 5.12.9 (Appimage)

ADDITIONAL INFORMATION
May or may not be the same issue in https://krita-artists.org/t/help-creating-pencil-brush/20064/6
Comment 1 Deif Lou 2021-05-03 13:05:01 UTC 
Git commit c40b4ca469da442d110e72cce307179039a276d0 by Deif Lou.
Committed on 03/05/2021 at 13:03.
Pushed by deiflou into branch 'master'.

Fix color dodge and color burn blend modes

Fixes incorrect handling of the 0/0 case and some artifacts in floating point
modes.

M  +60   -22   libs/pigment/compositeops/KoCompositeOpFunctions.h

https://invent.kde.org/graphics/krita/commit/c40b4ca469da442d110e72cce307179039a276d0