[cairo] Struggling with subpixel text (last blocker for 1.8)

Bill Spitzak spitzak at thefoundry.co.uk
Fri Oct 3 19:02:44 PDT 2008

"subpixel rendering" is not just for fonts. It can certainly be used for 
antialiasing of everything else Cairo draws. For that reason it makes a 
lot more sense for Cairo to be doing it, not FreeType. All that is 
needed from FreeType is images at a higher resolution (the input to the 

Therefore, whatever the legal ramifications, this certainly should be 
part of Cairo and turned on/off in it.

I believe you can avoid the patent by not filtering. This produces very 
annoying color fringing. You can also use an error-diffusion method to 
distribute the colors. Another technique I saw was to only use two 
"subpixels", one of them is green and the other is magenta, this can 
actually produce sharper images, and avoids the patented filter.

Bill Spitzak, Senior Software Engineer
The Foundry, 618 Hampton Drive, Venice, CA, 90291, USA
Tel: +1 310 399-4555 * Fax: +1 310 450-4516 * Web: www.thefoundry.co.uk
The Foundry Visionmongers Ltd * Registered in England and Wales No: 4642027

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