Keith Packard wrote:
> I wonder how much this has to do with our alpha composition working in
> linear value space instead of linear intensity space. One way to test
I think I shouldn't call it "alpha correction". Instead, "inverse-gamma
correction" is a better term, since normal "gamma correction" uses LUT
p' = 256 * (p/256) ^ gamma; (gamma <= 1)
When I used the word "alpha", I never thought of "alpha composition"
as used in your RENDER extension. In fact, the screen shots in my
previous message are generated by FT2 ft2demos' ftview which doesn't
use Xft at all.
As you suggested, I generated another set of screen shots. This time
they do use Xft: I am using xterm as
xterm -fa "AR PL SungtiL GB" -fs 12
for black text on white background and
xterm -r -fa "AR PL SungtiL GB" -fs 12
for white text on black background.
The same free Arphic SungtiL font is used as before. I put the screen
shots at
http://oto.sourceforge.net/xterms/index.html
For some reason, the same 12 point font, Xft showing it much bigger
than ftview. Let me know if you need anything else.
Raph Levien wrote:
> I can give a few datapoints, however, for newer renderers. Mac OS X
> does direct aa rendering (in other words, no quantization to, say, 1/4
> pixel), no hinting, and no gamma adjustment. Generally, the results
> are good, primarily due to factors other than the font rendering
> technology itself. For one, the entire desktop is rendered quite
> softly, so the relative lack of contrast for the fonts is not so
> noticeable. For another, Apple has chosen fonts and weights that work
> well antialiased. Sans serif fonts, with relatively uniform stroke
> weights, generally render better than serif fonts. The primary UI
> font, Lucida Grande at (I believe) 13.6 pixels, has a lowercase "l"
> width of about 1.17 pixels. This is enough to give reasonable
> contrast.
I'am pretty much doing similar things on my desktop now in order
to get good looking result. No hinting because anti-alias with
hinting looks worse for Chinese characters. Maybe this is because
FT2's hinting processor is not tuned for Chinese as stated in
their FAQ. I also need to choose a Heiti Chinsese font (sort of
like Helvetica font for English, sans serif and bold).
> As an aside, Mac OS X generally ignores instructions (hints). The
> exception is when you explicitly request non-aa rendering. In this
> case, hint processing is quite buggy. The evil PMingLiU.ttf font is a
> good test case for this.
Again, my experience/preference is also that for AA rendering, no hinting.
Not only that, for AA rendering, not using embeded bitmap font even if it
is available. FT2 allows those controls though its API but Xft doesn't
expose them to end user. Maybe it is too much for asking Xft to provide
those fine controls. Appalling, isn't it?
As of MingLiU.ttf, I found it simply doesn't work without turning on
TT_CONFIG_OPTION_BYTECODE_INTERPRETER. Unfortuately these days, major
distros leave it off by default. After turning it on, outline hinting or
not doesn't make any differnce. I don't know why. I just find that
out by playing "ftview".
Regards,
Yao Zhang
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