[Freetype] Re: [Render] Arial ttf - bad rendering of some glyphs

[David Turner]

Hello Vladim,

Vadim Plessky a écrit :
> 
> The most unpleasant rendering is with "э"
> Also, "а" and "в" have some *dirty* inside internal contours. Note that it's
> visible only on several specific pt sizes.
> For example, I am writing this mail in KMail, and both "а" and "в"look ok
> (Arial 11pt) while  "э" still has problems. But it looks different on web
> page due to different font size.
> (CSS page for that page is http://www.gazeta.ru/hrg.css)
> 
> In general, I think rendering quality for Arial with AA enabled is *better*
> than in Windows 98.
> If only errors specified above could be corrected...
> 
> I would appreciate any input on this subject.

I have currently no access to any Linux machine, so I can only
comment on the PNG you attached with your post.

The images you see are the direct result of the TT hints contained
in the Arial font file, since you enabled the auto-hinter.

There are great chances that these hints were specifically written
for monochrome rendering, not anti-aliased one.

(note that on my Win98 machine, the text always appears monochrome,
 not anti-aliased, at 11 pt/96 dpi)

Arial isn't actually the only Microsoft font that shows this kind
of descrepancies with the high-quality anti-aliasing performed by
FT2, which uses an analytical algorithm. For example, the "z" of
Times Italic doesn't show any diagonal due to improper hints at
some relatively small point sizes..

There is nothing that can be done to solve this specific problem,
unless you change the hints within the fonts. Another solution is
to use the auto-hinter, but results are rarely as pleasant as the
original (and I'm working on this btw)

What you can do however, is disable anti-aliasing for small point
sizes. You'll get results that should match Windows output (unless
you find a really weird bug in FT ;-)

Note that, the "bad hints" problem also appears often when trying
to render a font with different resolutions in X and Y. The
auto-hinter is even capable of beating the truetype interpreter
in these cases, how weird :o)

Regards,

- David