Bug 455106

Summary: Value (HSV) blend mode changes saturation unexpectedly
Product: [Applications] krita Reporter: Yu-Hsuan Lai <raincolee>
Component: Color modelsAssignee: Tiar <tamtamy.tymona>
Status: ASSIGNED ---    
Severity: normal CC: halla, tamtamy.tymona
Priority: NOR    
Version First Reported In: 5.0.6   
Target Milestone: ---   
Platform: Other   
OS: Other   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Yu-Hsuan Lai 2022-06-10 03:12:35 UTC 
SUMMARY
"Value" blend mode (under HSV section) should only change value.

STEPS TO REPRODUCE
1. Create a layer and fill it with hsv(0, 100, 50) (a dark red color)
2. Create another layer above it, fill it with hsv(0, 0, 100) (pure white)
3. Change the top layer's blend mode to "Value"

OBSERVED RESULT
The blended color is hsv(0, 49.8, 100) (pink)

EXPECTED RESULT
The blended color is hsv(0, 100, 100) (pure red)

SOFTWARE/OS VERSIONS
Krita 5.0.6
probably all platforms

ADDITIONAL INFORMATION
I know other software has similar behavior. However, I still consider it a bug. Krita's "Value" blend mode is explicitly under "HSV" section, which implies it should change the value and value only, according to HSV color model. It shouldn't change saturation somehow. If I'd like to change lightness, I'd use "Lightness" blend mode (under HSL section). "Value" shouldn't try to be smart like this.
Comment 1 Halla Rempt 2022-06-15 10:17:00 UTC 
Gimp produces the right results, but Krita imports the psd created in gimp with luminosity instead of the hsv value blending mode, but that's because psd doesn't _have_ the value blending mode. Or, at least, Photopea doesn't. Setting the blending mode to value creates the effect you noted, so I can confirm the bug.