Bug 473063

Summary: Channels in CMYK have inverted maps
Product: [Applications] krita Reporter: keyth_qcfx2 <keyth2363214>
Component: DockersAssignee: Dmitry Kazakov <dimula73>
Status: ASSIGNED ---    
Severity: minor CC: dimula73, griffinvalley
Priority: NOR Keywords: regression
Version First Reported In: 5.1.5   
Target Milestone: ---   
Platform: Microsoft Windows   
OS: Microsoft Windows   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: inverted representation compared to the pixel data

Description keyth_qcfx2 2023-08-06 05:16:05 UTC
Created attachment 160774 [details]
inverted representation compared to the pixel data

When you see C=0 M=0 Y=0 K=0 it will be represented as white even though it has no selection of no channel.
this inverts selection expectation because when C=1 on the cyan channel it will become black with selection.
by consequence the map of Key will look like a normal grayscale version of the map even though it is selecting black not white.


STEPS TO REPRODUCE
1. open a image in CMYK color model
2. verify the amount of any pixel compared to the specific solor selector and the amounts are inverted

OBSERVED RESULT
Alot of cyan will be rendered as black instead of white

EXPECTED RESULT
The visual representation of all maps following the same rule. 
white -> selected = 1 or  255
black -> selected = 0

SOFTWARE/OS VERSIONS
Windows: 10
Qt Version: 5.12
Comment 1 wolthera 2023-10-18 11:38:45 UTC
I can confirm, it also affects the seperate image dialog, and it seems to be caused by the 'subtractive blending for CMYK', when setting that to 'additive', it starts to work as expected. Dmitry's already assigned himself, it seems.
Comment 2 Dmitry Kazakov 2024-08-22 16:39:02 UTC
Remove triaged keyword from CONFIRMED bugs