https://bugs.kde.org/show_bug.cgi?id=444439
Bug ID: 444439
Summary: Floating-point HDR colors get clipped from painting,
layer blending or color space conversion
Product: krita
Version: git master (please specify the git hash!)
Platform: Compiled Sources
OS: All
Status: REPORTED
Severity: normal
Priority: NOR
Component: Color models
Assignee: krita-bugs-n...@kde.org
Reporter: manuel.snudl.zeid...@gmail.com
Target Milestone: ---
SUMMARY
I'm trying the newest Nightly e2a04dd823 on Windows and it seems there are now
several problems with clipping HDR colors.
If the document is in 32-bit float and uses any gamut other than the default
sRGB-g10, it's not possible to get color values above 1.0 in any color channel
anymore, either from paint brushes or stacking layers in Addition blend mode.
If the document is converted to a different profile like sRGB-srgbtrc or
ACEScg-g10, the colors also get clipped to a max of 1.0 in the process.
Additionally, very saturated high-brightness colors get visually shifted in the
conversion.
These problems don't seem to happen with 16-bit float, but converting to 8 or
16-bit integer will also result in those color shifts, so it's not even
possible to guarantee the visual appearance of the image for export in an SDR
format anymore.
STEPS TO REPRODUCE
Conversion:
1. Create a document in 32-bit float and default sRGB-g10
2. Paint with a brush set to Addition, or stack layers in Addition mode
3. Use Image > Convert Image Color Space and choose a different profile
4. Check the resulting color channel values from the canvas
Blending:
1. Create a document in 32-bit float, choose a different profile than sRGB-g10
2. Paint with a brush set to Addition, or stack layers in Addition mode
3. Merge and check the resulting color channel values from the canvas
OBSERVED RESULT
Loss of color information, potential visual shifts.
EXPECTED RESULT
Retention of the HDR colors.
SOFTWARE/OS VERSIONS
Krita 5.1.0-prealpha (git e2a04dd) on Windows 10
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