Re: [ft-devel] State of autohinter stem darkening

[Nikolaus Waxweiler]

> There is a cool image attached to this bug report:
> https://bugreports.qt.io/browse/QTBUG-41590
>
> Gamma correction makes black text lighter and white text heavier,
> i.e., has opposite effects, i.e., you cannot use one universal value.

Hold on, that's intended: "Gamma 1.8, darkened" is *exactly* what we 
need! It might look alien to you, but that's partly because we've been 
looking at non-corrected glyphs for so long in Linux land that we think 
it's how things must be. You'll get used to the gamma-corrected look 
quickly :)

Non-gamma-corrected dark text on light background is too heavy and light 
text on dark background too light. Gamma correction/linear 
alpha-blending equalizes this to the eye. Look at 
https://imgur.com/a/5YzVM, first pic: gamma correction, second pic: no 
gamma correction. Note the lightness, color-fringing and pixelyness. 
Also note how red text on green background in the bug report image looks 
the cleanest in "Gamma 1.8" and "Gamma 1.8, darkened". So yes, gamma 
correction should be done universally.

The stem darkening done by the CFF driver and now the autohinter counter 
the lightness of gamma-corrected text (compare "Gamma 1.8" and "Gamma 
1.8, darkened"). That's the entire point of the feature. Mac OS X is 
probably doing it that way (Dave? ;)).