Bug 442081

Summary:	The algorithm of "Hard Mix (Photoshop)" is different from Photoshop
Product:	[Applications] krita	Reporter:	thetwo <thetwo222>
Component:	Color models	Assignee:	Krita Bugs <krita-bugs-null>
Status:	ASSIGNED ---
Severity:	normal	CC:	halla
Priority:	NOR
Version First Reported In:	5.0.0-beta1
Target Milestone:	---
Platform:	Microsoft Windows
OS:	Microsoft Windows
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	difference

Description thetwo 2021-09-06 15:12:51 UTC

SUMMARY
krita did not further classify and calculate when base color + mixed color = 255.
Post on the KA forum:
https://krita-artists.org/t/about-hard-mix-photoshop/28640


STEPS TO REPRODUCE
1. Paint with red (255 0 0)
2. Create a white layer (255 255 255) and place it below
3. Toggle "Hard Mix (Photoshop)"


OBSERVED RESULT
Red still exists

EXPECTED RESULT
In ps and csp, it is white

Comment 1 thetwo 2021-09-06 15:15:30 UTC

In photoshop, the mixed results of (127 0 0)-(128 0 0) and (128 0 0)-(127 0 0) are also different. But it is the same in krita.

Comment 2 thetwo 2021-09-06 15:16:30 UTC

Created attachment 141338 [details]
difference

Comment 3 Halla Rempt 2022-07-05 09:26:50 UTC

I see from the k-a thread that you already have a fix. Could you make a merge request?

Comment 4 thetwo 2022-07-05 09:50:31 UTC

(In reply to Halla Rempt from comment #3)
> make a merge request?
Sorry, this is beyond my knowledge…

Comment 5 Bug Janitor Service 2023-06-23 12:47:53 UTC

A possibly relevant merge request was started @ https://invent.kde.org/graphics/krita/-/merge_requests/1835