[cairo-bugs] [Bug 10301] LCD filtering patch

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Aug 5 07:12:25 PDT 2008


--- Comment #55 from Sylvain Pasche <sylvain.pasche at gmail.com>  2008-08-05 07:12:18 PST ---
I've pushed an updated version on http://spasche.net/git/cairo.git (thanks
James for the updated patch, that helped me for merging).

I've added a new patch with tests (text-lcd-filter-*). I had to update the
text-antialias-subpixel reference image now that the subpixel antialiasing uses
FreeType. (I didn't update/add quartz reference image, should I do that?).

I had a quick look for the Windows / OS X story, I didn't find APIs for
controlling the LCD filter but it is possible I missed something.

On Windows, the LCD filtering is handled by ClearType. The ClearType settings
are stored in the registry (HKCU/Control Panel/Desktop/FontSmoothing* entries).
The LOGFONT structure which defines the attributes of a font has a lfQuality
member to select if ClearType should be used for the font. So it doesn't look
like to be possible to change the LCD filtering algorithm through the font API.

For OS X, outside of the
CGContextSetAllowsAntialiasing/CGContextSetShouldAntialias methods, I didn't
find something that looks like to control the type of LCD filter.

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