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

[Dave Arnold]

On 10/22/2015 9:00 AM, Nikolaus Waxweiler wrote:
> > - I think stem darkening should be tested without gamma applied for
> > many reasons. Your monitor might have additional gamma correction
> > settings, which might be different from mine. Gamma correction works
> > against you when you render light text on dark background (I wish
> > ftview could do that). I think that the whole point of stem darkening
> > is that it is better than gamma correction in this respect.
>
> The code in FT does nothing with gamma actually. That's a separate step a 
> rendering library should do to the bitmaps it gets from FreeType. The 
> screenshots I provided so far were just made with a hacked pixman ;)
>
> And gamma correction leads to better results with light text on dark background 
> as far as I can see: https://bel.fi/alankila/lcd/
>
> Stem darkening is intended to work hand-in-hand with gamma correction. You can 
> run without it, sure, but it won't look too pretty and might exacerbate the 
> already present color-fringing, blotchiness and pixelness of glyphs ;)
I completely agree with Nikolaus. To state it a different way, correct anti-aliasing 
requires that the compositing (alpha blending) is done in a linear color space. The 
"gamma correction" step is used to convert from and to the user's color space. 
The gamma used could be different on some systems, but it is a reasonable assumption that 
the user's monitor gamma is close to sRGB. Otherwise, photographs, images and video would 
look wrong.