Bug 444660

Summary: The result of the color adjustment curve under the 16 bit channel is incorrect
Product: [Applications] krita Reporter: killy <80536642>
Component: FiltersAssignee: Krita Bugs <krita-bugs-null>
Status: CONFIRMED ---    
Severity: normal CC: halla
Priority: NOR    
Version First Reported In: 5.0.0-beta2   
Target Milestone: ---   
Platform: Microsoft Windows   
OS: Microsoft Windows   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description killy 2021-10-30 13:22:50 UTC 
SUMMARY
When the color profile of the canvas is 16-bit lrgb(gamma 1.0), the result of the color adjustment curve is the same as that when the color profile is 8-bit srgb(gamma 2.2). The result is not calculated according to the lrgb value, but according to the srgb value.

STEPS TO REPRODUCE
1. Create a canvas with 16-bit lrgb color profile
2. Draw any color and select anThe adjustment results of hue, saturation or brightness channels are the same in differe area with the selection tool, open the color adjustment curve in the color filter, select the lightness channel, and adjust the rightmost end of the curve to any value
3. Convert the canvas to an 8-bit srgb color profile file, and repeat the second step. It is found that the adjustment results are the same for the same color.

OBSERVED RESULT
The adjustment results using hue, saturation or lightness channel for the same color are the same in different color profiles

EXPECTED RESULT
In a canvas with a 16-bit lrgb color profile, when adjusting the color using the hue, saturation or lightness channel of the color adjustment curve, the result should be the same as that of the cross channel color adjustment curve using the same channel for the adjustment channel and the drive channel, not the same as that of the canvas with an 8-bit srgb profile.

SOFTWARE/OS VERSIONS
Windows: 5.0.0-beta2

ADDITIONAL INFORMATION
Comment 1 killy 2021-10-30 13:26:50 UTC 
Sorry, the "brightness" should be "lightness". I used translation software, so there was an error.
Comment 2 killy 2021-11-04 07:15:00 UTC 
After some tests, I found that this bug only occurs when the canvas color profile file is 16-bit and the lightness channel is adjusted. In addition, it also occurs in the V channel, I channel, L channel and Y channel in the HSV adjustment filter. There are no bugs in the hue and saturation channels. I don't know why, or maybe it is designed like this?