Bug 306251

Summary:	Font anti-aliasing sub-pixel defect in GIMP 2.8.x with KDE
Product:	[Applications] systemsettings	Reporter:	Tyson Tan <tysontanx>
Component:	general	Assignee:	Unassigned bugs mailing-list <unassigned-bugs>
Status:	RESOLVED DOWNSTREAM
Severity:	minor	CC:	cfeck
Priority:	NOR
Version:	unspecified
Target Milestone:	---
Platform:	unspecified
OS:	Linux
URL:	https://bugzilla.gnome.org/show_bug.cgi?id=683330
Latest Commit:		Version Fixed In:
Attachments:	Font anti-aliasing sub-pixel defect in GIMP 2.8.x with KDE Correct text antialias after applying the workaround.

Description Tyson Tan 2012-09-04 14:11:30 UTC

Summary:
In GIMP 2.8.x on a system with KDE installed, after making change to KDE's font anti-alias settings, inserting white texts with anti-aliasing option over colorful background will produce greenish sub-pixel defect around the texts. Such defect remains after you flatten the image and will be saved in the document.

I don't know if this is a GIMP bug itself, but since the trigger and workaround is within KDE System Settings, I think I should report this problem here as well.

Reproducible: Always

Steps to Reproduce:
1. Ubuntu 12.04.1 LTS with KDE 4.8.5 from Kubuntu PPA installed.
2. Either log in Unity or KDE desktop.
3. In KDE System Settings -> Application Appearance -> Fonts -> Use anti-aliasing -> Enabled -> Configure -> Use Sub-Pixel Rendering, Hinting Type = None
4. Start GIMP, make a red pure background.
5. Insert some white texts over the red background, make sure antialiasing is on.
6. Notice greenish defect around the texts.
7. Select the texts, turn antialiasing off, those defect will disappear.
Actual Results:
The sub-pixels are always greenish unless the texts are black.

Expected Results:
The sub-pixels should be blended with the background color.

Workaround:
KDE System Settings -> Application Appearance -> Fonts -> Use anti-aliasing -> Enabled -> Configure -> Uncheck everything

You may apply this workaround when GIMP is running, the effect will show immediately when you select the defect texts in GIMP, then turn antialias off and back on.

Sometimes such defect won't show up, however I've been plagued by this problem since the day GIMP 2.8 is out. I've encountered such defect on the following configurations more than a few times. On Ubuntu 12.04.1 + KDE 4.8.5 + GIMP 2.8.2 this problem show up everytime after I changed KDE font anti-alias settings.

Ubuntu 12.04 + KDE 4.8.4 + GIMP 2.8.0
Ubuntu 12.04 + KDE 4.8.4 + GIMP 2.8.2
Ubuntu 12.04 + KDE 4.8.5 + GIMP 2.8.2
Ubuntu 12.04 + KDE 4.9.0 + GIMP 2.8.0
Ubuntu 12.04 + KDE 4.9.0 + GIMP 2.8.2
Ubuntu 12.04.1 + KDE 4.8.5 + GIMP 2.8.2

All of them have QT 4.8.2 (libqt libraries) installed.

Comment 1 Tyson Tan 2012-09-04 14:23:23 UTC

Created attachment 73646 [details]
Font anti-aliasing sub-pixel defect in GIMP 2.8.x with KDE

Font anti-aliasing sub-pixel defect in GIMP 2.8.x with KDE

Comment 2 Tyson Tan 2012-09-04 14:23:58 UTC

Created attachment 73647 [details]
Correct text antialias after applying the workaround.

This screenshot is taken from the same session as the defect one, just after
applying the workaround, it was restored realtime. No restarting GIMP is
needed.

Comment 3 Christoph Feck 2012-09-04 21:42:18 UTC

See https://bugzilla.gnome.org/show_bug.cgi?id=657047