Bug 442209

Summary:	LittleCMS optimization is cause severe artifacts in Transform tool
Product:	[Applications] krita	Reporter:	Tyson Tan <tysontanx>
Component:	Tools/Transform	Assignee:	Krita Bugs <krita-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	amy, halla
Priority:	NOR
Version First Reported In:	5.0.0-beta1
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Krita 5.0 Transform tool artifacts

Description Tyson Tan 2021-09-09 09:06:06 UTC

Krita's Transform tool causes severe transparent artifacts that actually rendered into the result. It only happens when the canvas behind the transformed layer has nothing to cover its transparent areas.

Steps to reproduce:

1) Open a JPG (which has only 1 layer)
2) Transform tool
3) Move or rotate the layer
4) Huge blocks of pixels goes in and out of transparency.
5) Hit Apply
6) The artifacts are rendered into the result.

* The transform tool is also very choppy now, which is a recent development.

Workaround:
1) Insert a layer below the transformed layer
2) Fill it with white
3) Transform
4) Now it doesn't generate artifacts, but still very choppy.

Tested with krita-5.0.0-beta1-92c6cb6-x86_64.appimage

Comment 1 Halla Rempt 2021-09-09 09:09:49 UTC

The transform tool now renders inside the layer stack, and that is slower. This cannot be made faster, sorry. You can re-enable the old behaviour in the settings. 

I cannot reproduce any artefacts when testing with a jpeg image of one layer.

Comment 2 Tyson Tan 2021-09-09 11:51:32 UTC

Created attachment 141420 [details]
Krita 5.0 Transform tool artifacts

After a little test, I've found that the issue is, again, LittleCMS optimization related.

When these options are on:
1) Use system monitor profile (I have one)
2) Allow Little CMS optimizations

It will cause all kinds of artifacts in almost every HUD elements on canvas. I think we should take look into this optimization a bit more...

Comment 3 Tyson Tan 2021-09-09 11:53:13 UTC

BTW, after setting Allow LittleCMS Optimizations, you must restart Krita to see the difference in case of the artifacts.

Comment 4 Halla Rempt 2021-09-09 11:53:27 UTC

Okay, the good news is that we're getting patches into lcms to fix those issues.

Cc'ing amyspark so this bug can be in the list of closable bugs once those fixes land in the deps build.

Comment 5 Tyson Tan 2021-09-09 11:57:35 UTC

Thanks! That's good to know.

Comment 6 Tyson Tan 2021-09-15 04:13:40 UTC

The bug has been fixed with the latest LCMS patches.