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Re: A supposedly patent-free suggestion/solution to the curious subpixel rendering in Fedora



On Sun, Mar 22, 2009 at 5:18 PM, Jud Craft <craftjml gmail com> wrote:
Hello there, thanks for reading.  This may be a bad place for this
post, I apologize if so.

Here's the problem, stated over and over throughout bad forum posts:
subpixel-rendering on Fedora is a little sub-par.  The chief reason
(from my lay perspective) is that it doesn't implement the various
cleartype-like filtering algorithms demonstrated in all sorts of
questionable patches, due to fear of patent-infringing on Microsoft's
Cleartype work.  This means Fedora's default subpixel-rendering is
full of color-fringes and in general less smooth than other algorithms
shown in (for example) Debian and Ubuntu.

Currently the only solutions are:

1.  Try out freetype-freeworld:  restores the bytecode interpreter to
Freetype and some adds filtering, patent-infringing, stuck in
RPMFusion, can't be merged into Fedora.
2.  Try out those peculiar cleartype-patches flying around the forums:
 you get all filtering functionality back, but again, patent
infringement.

Okay, here's something different.  Check this out:  Qt (that other GUI
toolkit) actually developed their own method to reduce the color
fringing on subpixel-rendering:
http://labs.trolltech.com/blogs/2008/09/01/subpixel-antialiasing-on-x11/

Qt is not perfect (their filter automatically locks you into
full-hinting on Qt 4.4, but that'll be fixed in 4.5), but their method
(without using any other patent-infringing algorithms) is very
beneficial.  You'll note their un-filtered examples look just as bad
as the current filtering in GTK in Fedora, while their fixed-examples
look pretty decent.

So here's the idea:  perhaps Fedora could petition Pango (I think
that's the system GTK uses to render glyphs) to include the
Qt-filtering style in their own upstream code.  This would mean that
both GUI toolkits on the Linux desktop would then have patent-free,
non-color-fringing, subpixel rendering by default.

And today currently, keep in mind that Qt on Fedora already has this
new filtering, so I don't think there are any patent-problems with it:
 Qt's solution seems to be a simple blur of their own ingenuity, and
nothing related to Cleartype.  (Otherwise Fedora wouldn't ship it, I'd
assume).

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A good idea yes, but the reason why Fedora and other USA-based distros have such bad font rendering is because the hinting algorithms in freetype are patented not by Microsoft, but by Apple. http://freetype.sourceforge.net/patents.html

Meh, ClearType is just the same as the subpixel hinting that is patented by Apple, just a different name.

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