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Re: Fonts readability (was: Arial vs. Helvetica.)




Le sextidi 16 thermidor, an CCXXV, rhkramer@xxxxxxxxx a écrit :
> > Even worse, the anti-aliasing is done wrong:
> > it is done without taking gamma correction into account. That means that
> > when 50% intensity is wanted, it produces 22% intensity instead:
> > black-on-white is too thick, white-on-black is too thin.
> 
> Thank you for confirming something I suspected for a long time.
> 
> Do you know what program(s) is responsibe for the anti-aliasing,
> against which a bug might be filed (or maybe a bug has already been
> filed)?

It is hard to tell, there are several components working together, and
they all will try to shift the blame to each other. I tried filling it
years ago, and it gave me that:

http://bugs.freedesktop.org/show_bug.cgi?id=13431

If somebody dares tell me that the way of reading text that I chose is
"wrong", I think it is worthless to try to discuss.

The components in play are:

- fontconfig: at some point, the user needs to be able to tell that
  gamma correction must be taken into account and what the gamma value
  should be. Despite what kp wrote, it belongs in fontconfig, just as
  much as lcdfilter or rgba.

- Freetype: it is the component that rasterizes the vector fonts,
  including anti-aliasing, so it would be an easy place to adjust for
  gamma. Unfortunately, Freetype does not know the color of the text and
  background, its output could be considered an alpha map.

- The X11 RENDER extension: it is the component that performs the alpha
  blending. It would be the correct place to implement the gamma
  adjustment. Unfortunately, it has no provisions to do so.

- Xft: it is the glue that holds everything together. I do not think it
  needs any work for this issue.

Good luck if you want to get things moving.

Regards,

-- 
  Nicolas George

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