Created attachment 161275 [details] blue umbrella with red tinted display STEPS TO REPRODUCE 1. Open a image in Krita 2. convert image into CMYK color model 3. through the channels docker isolate until only one channel is active OBSERVED RESULT the map has a destinctive red hue EXPECTED RESULT black and white map SOFTWARE/OS VERSIONS Windows: 10 Qt Version: ADDITIONAL INFORMATION other softwares dont seem to have the red tint while on CMYK documents.
The bug happens because the way how Krita generates "gray" preview of a single channel is by resetting all the channels to the same value. In theory, it should become "gray", but for non-ideal profiles it may cause weird tints. The proper solution would be to change the output color space of the tiles when doing channel preview, e.g. to RGB, when R=G=B is more or less gray...
Or maybe setting the black channel to the values of the selected one and the others to 0?
> Or maybe setting the black channel to the values of the selected one and the others to 0? That is not very correct for CMYK from the technical point of view, because the profile may indirectly impose "black level limitation" which we would break. Though, it such case, painting directly in CMYK will also break this rule...