Bug 432289

Summary: Anti-aliasing is applied when using pressure sensitive stylus, with anti-aliasing unchecked
Product: [Applications] krita Reporter: Domarius <domarius>
Component: Brush Engine/ShapeAssignee: Krita Bugs <krita-bugs-null>
Status: RESOLVED INTENTIONAL    
Severity: normal CC: griffinvalley
Priority: NOR    
Version First Reported In: 4.4.2   
Target Milestone: ---   
Platform: Manjaro   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Brush stroke that starts aliased, but becomes anti-aliased as it gets smaller.

Description Domarius 2021-01-29 21:47:49 UTC
Created attachment 135292 [details]
Brush stroke that starts aliased, but becomes anti-aliased as it gets smaller.

SUMMARY
When you don't want any anti-aliasing (or should I say, when you want aliasing), and you uncheck "Anti-aliasing" in the brush settings, drawing with the mouse is fine. But drawing with a stylus on a graphics tablet and allowing the pressure to control the size, will introduce anti-aliasing when the brush shrinks below a certain size.

This causes pixelated halos when using the fill tool.

STEPS TO REPRODUCE
1. Click the "Edit brush settings" icon
2. Uncheck "Anti-alias"
3. Draw on the canvas using a stylus and vary the pressure to control the size

OBSERVED RESULT
The brush stroke becomes anti-aliased below a certain size.

EXPECTED RESULT
The brush stroke should never become anti-aliased when anti-alias is unchecked.

SOFTWARE/OS VERSIONS
Windows: Unknown
macOS: Unknown
Linux/KDE Plasma: Confirmed
(available in About System)
KDE Plasma Version: 5.20.5
KDE Frameworks Version: 5.79.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION
Comment 1 wolthera 2021-01-29 21:52:23 UTC
Hi,

What you are seeing is not anti-aliasing, but rather a side effect of our subpixel coordinate system. If you want the edges to be hard, check the 'sharpness' option.

https://docs.krita.org/en/reference_manual/brushes/brush_settings/options.html#sharpness
Comment 2 Domarius 2021-01-30 02:51:34 UTC
Oh, so it would seem.  Certainly not an obvious thing; basically getting pixel sharp strokes is a two step process in Krita.  I asked on the forum weeks ago and didn't get a response, and I figured it has to be a bug.

Glad to see it works after all.