Re: [ft] Gamma (?) huge difference between FreeType and others (OS X, or even FreeType based MacType)

[Werner LEMBERG]

> Now I use the same fonts to compare them again.

Thanks, however...

> Compare them side by side,
> CJK:
> https://i.imgur.com/eXOpUPN.png

... the font sizes are not identical, unfortunately.  Doing a blink
comparison of the first body text line (starting with `李') I see that
the Linux version is 1ppem smaller.  This makes it very hard to
exactly compare rendering differences.

> Latin:
> https://i.imgur.com/3huCFdq.png

The same thing.

> With the comparisons, you can clearly see the "color" difference
> between FreeType and other two.  By my eye, it looks like OS X and
> MacType both font rendering's "color" have a little bit "red"
> inside, or just simply say that looks more "red" (or "purple red")
> than Linux.  Only Linux font rendering's "color" still looks "blue".
> By "color", it's because I still don't know what really called is.
> I have been searching a lot of articles about font rendering in the
> past week, but none of them can helps me out with this "color"
> issue.  I was thought that it probably could be "Subpixel rendering"
> related, but still not sure.

Your guess is right, I believe, being related to the applied subpixel
color filter.  The original one developed by Microsoft is patented
(aka. ClearType), thus not enabled on various GNU/Linux distributions,
AFAIK.  The legacy color filter that FreeType provides is rather poor,
and it seems that nobody has yet come up with a better one for X11.
[List readers: In case I'm wrong, please correct me!  And I would be
really glad if I'm wrong...]

> I'm also wondering since MacType is FreeType too, which means that
> FreeType can did the right "color" of the font rendering.

Maybe they simply using a better color filter.


    Werner