Technical question on font rendering (gamma correction)

Allan Sandfeld Jensen kde at
Mon May 31 14:43:01 BST 2021

On Donnerstag, 27. Mai 2021 16:53:26 CEST Richard Lane wrote:
> Hi,
> Since Qt 5.9 .otf fonts have been rendered with alpha-blending and gamma
> corrected in Qt apps / environments. The only other rendering engine to do
> this is Skia (used in Chrome browser etc.). I have a hardware calibrator
> device for my monitor.
> My question is two-part:
> 1) What real monitor gamma value does KDE assume to do the gamma correction?
> 2.2? 2) I have noticed that a slightly darker gamma on my monitor is
> preferable, as the desktop looks slightly washed out at the default. Is it
> better to: a) calibrate my monitor to 2.4 instead of 2.2

I believe the gamma is currently using a value of 1.7. This is also similar to 
what Skia does. I find using the real gamma values significantly changes the 
perceived boldness of the fonts (much like using gamma correction on TTF 
fonts). The font gamma value can however be overwritten by the QPA plugin, but 
is currently global, not per screen.

There are interconnected problems here with old fonts specifically having been 
designed to be rendered using the old wrong methods, and users having chosen 
fonts and designs calibrated to look good with the old wrong methods. Both 
means correcting past mistakes results in a perceived immediate degradation of 
font rendering.


More information about the kde-devel mailing list