Bug 430372

Summary:	HSV Filter degrades quality of CMYK images
Product:	[Applications] krita	Reporter:	Dmitry Kazakov <dimula73>
Component:	Filters	Assignee:	Krita Bugs <krita-bugs-null>
Status:	CONFIRMED ---
Severity:	normal	CC:	griffinvalley
Priority:	NOR
Version First Reported In:	git master (please specify the git hash!)
Target Milestone:	---
Platform:	Other
OS:	Other
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Dmitry Kazakov 2020-12-14 11:50:19 UTC

SUMMARY

When opening HSV filter on an CMYK image the quality of the image degrades right after opening the filter, without changing any controls.

STEPS TO REPRODUCE
1. Create/open any colorful image in CMYK space.
2. Open HSV filter
3. The image starts looking desaturated, even though you didn't change any controls

The problem is because HSV filter converts the image into RGB before processing. I guess we should somehow use CMYK-complements instead of RGB conversion to make this filter work correctly. CMYK-complements are defined in PDF specification for blending modes, so that it should work fine with the filters as well.

This bug is very related, but different:
https://bugs.kde.org/show_bug.cgi?id=424525

Comment 1 wolthera 2021-09-08 08:56:05 UTC

I guess I'll confirm this, but we're going to need more research linked to this...

Comment 2 Dmitry Kazakov 2024-08-22 16:38:36 UTC

Remove triaged keyword from CONFIRMED bugs