Bug 306251

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.