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Re: Freetype Development


From: Werner LEMBERG
Subject: Re: Freetype Development
Date: Sat, 14 Mar 2020 17:15:35 +0100 (CET)

> Recently some ClearType byte code interpreter patents have
> expired. Subpixel rendering ones, not quite. Most of them expired in
> November last year, but these are still active until end of July:
> 
> https://patents.google.com/patent/US6282327
> https://patents.google.com/patent/US6393145
> https://patents.google.com/patent/US6624828
> https://patents.google.com/patent/US6973210

Thanks for telling!

> When will we get subpixel rendering to become the default in
> FreeType?  Any Plan about these changes?

What exactly do you mean with `default'?

Note that FreeType already supports a subpixel rendering mode even if
the patented ClearType filtering technology is disabled, using a
different algorithm for the RGB channel distribution.  From the 2.8.1
announcement:

  - By default, FreeType now offers high quality LCD-optimized output
    without resorting to ClearType techniques of resolution tripling
    and filtering.  In this method, called Harmony, each color channel
    is generated separately after shifting the glyph outline,
    capitalizing on the fact that the color grids on LCD panels are
    shifted by a third of a pixel.  This output is indistinguishable
    from ClearType with a light 3-tap filter.


  Werner



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