[Pixman] Proposal for pixman's glyph rendering: alpha correction

Behdad Esfahbod behdad at behdad.org
Fri Mar 15 01:30:22 PDT 2013

On 13-03-13 09:59 AM, Antti Lankila wrote:
> I have a suggestion for getting sRGB-like text rendering without having sRGB alpha blending primitive. It's based on adjusting the alpha values of the glyph masks based on text foreground color without knowledge of the background color. I generated a writeup of it here:
> https://bel.fi/alankila/lcd/alpcor.html
> This looks like something that pixman's new glyph rendering code might consider doing. Thoughts?

Hi Antti,

This is indeed interesting, and very similar to what Skia does.  I believe
Skia has five buckets for the alpha, and ignores the middle bucket.

That said, it resulted in really bad color fringing in bright-on-black text in
Chromium.  I'll try to find the bug.  But then, Skia is doing a lot more stuff
with the glyph masks, so I wouldn't be surprised if it was a Skia screwup.

Do you have before / after images?



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