[Devel] freetype LCD filtering

[Sebastien Kunz-Jacques]

Hello everybody,

I am new to this list and I am not fully aware of all
the developpement going on around freetype; nor do I
have (yet!) a good understanding of the structure of
the code. 

I have implemented a simple algorithm for performing
LCD linear filtering on an antialiased image computed
in horizontal LCD mode. Instead of modifying the
library, I simply implemented the filtering in ftview.
This work raised several questions:

- In view of the insertion of this filtering feature
in the freetype lib, are there some changes to be done
on the application side to be able to display 24-bit
RGB glyph pictures ? Is anybody aware of applications
requiring only a minor rework ?
- In experiencing with a nonlinear filtering aimed at
increasing glyph contrast,  I noticed that the
antialiasing algorithm used by freetype changes
between 34 and 35pt : exact coverage for ppem<35,
supersampling above. the supersampling gives
lower-quality results than the exact coverage algo;
where do I have to modify the freetype source in order
to use the exact coverage algorithm everytime? What is
the order of magnitude of the performance loss?

If someone is interested by the filtering code, I can
post it on the list.

Sébastien Kunz-Jacques

Thanks, 


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