Re: [Freetype] Freetype fonts not drawn as well as Windows...

[David Turner]

Hello Paul,

  thanks for the new bitmaps, I'll try to comment them:

> 
> http://ppedriana.homeip.net/Misc/Arial7HintAA.gif
>
Well, this is normal and caused by the fact that this font
is not hinted for anti-aliased display (at this small pixel
size, Windows does not display AA text, but monochrome one)

the old betas of FT2 had a different anti-aliasing algorithm
that happened to produce better results for certain cases like
this one. Unfortunately, it also gave rather unpleasant results
with a lot more other glyphs, which is why it has been replaced
with the new renderer..

And in case you're wondering, I don't think it's possible to
"marry" the algorithm, they're based on _completely_ different
concepts..

if you want to draw as well as Windows, you'll probably need
to use monochrome bitmaps here..

 
> http://ppedriana.homeip.net/Misc/Arial13HintNoAA.gif
>
This one is different. I do not remember if the old beta did
this too or not. If not, it probably boils down to some changes
to one of the algorithm used in the TrueType interpreter.

Could you try to define FT_CONFIG_OPTION_OLD_CALCS in
"include/freetype/config/ftoption.h" and see if this changes
the results ??

All I can say is that some operations supported by the TrueType
bytecode specification are highly dependent on the "accuracy"
of fixed-point operations (like mul, div and sqrt), and that
differences might be noticed in certain specific cases, due to
the fact that we probably don't use the exact same routines
than the original Apple or Microsoft engines.

 
> http://ppedriana.homeip.net/Misc/Arial12NoHintNoAA.gif
>
Well, this one has hinting disabled, so you should expect
something as bad, don't you ??

 
> It happens with some other fonts but with similar results.
> Pixels that should not be drawn in monochrome are being
> drawn, and pixels that should be light in anti-aliased mode
> are too dark. Windows does not have these problems.
> I can post more pictures from other fonts and characters
> if anybody would like. Some other examples I've seen are
> more obvious than the ones above, but it would take me
> a little longer to re-find them.
>

I think it's important to compare what's comparable, i.e.
monochrome glyphs with FreeType _and_ Windows, anti-aliased
ones on FreeType _and_ Windows..

Note that the anti-aliased renderer used by FreeType is far
different from the one used in Windows (which is limited to
5 levels of "gray").

For example, the diagonal of "z" or "Z" in certain fonts, like
Times New Roman Italic, disappears with FreeType. Unfortunately,
this is normal, and due to the fact that hinting applied to the
glyph simply makes a zero-width diagonal (which translates to
"void" pixel with an analytical algorithm as the one we use).

simply put it, the fonts were not hinted for high-quality
anti-aliasing..

Regards,

- David

 
> Paul
> 
> _______________________________________________
> Freetype mailing list
> address@hidden
> http://www.freetype.org/mailman/listinfo/freetype