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RE: [ft] Oversized "O"

From: Turner, David
Subject: RE: [ft] Oversized "O"
Date: Mon, 10 Oct 2005 13:55:34 +0200

Hello Hanno,

I think I have an answer to your question:

- first of all, the behaviour *only* happens when
  using the bytecode interpreter. this implies that:

   - you're not using the stock FreeType installation
     of your Ubuntu distribution :o)

   - what's you're seeing is the result of the
     instructions located within the font file, this 
     problem is also very similar to many oddities
     exposed by TrueType hinted fonts, like disappearing
     diagonals ('z' of Times New Roman Italic), or small
     holds in the legs of many "k"s.

   - there is little we can do, except if we want to
     basically hack the outlines at runtime when we detect
     certain glyphs, at certain times, in certain font
     files, if only anti-aliased hinting is wanted.

     something that I'm not ready to do at the moment.

   - note that the overlap doesn't appear in monochrome
     rendering mode, because while the same vector outlines
     are used in both AA and mono modes, the overlaps are
     too small to turn lower or upper mono pixels on.

- When configuring Windows to perform "normal" anti-aliasing 
  (i.e. not ClearType), you'll notice that small text sizes are
  still rendered in monochrome.

  I believe that the MS engineers deliberately did this to avoid
  the problem described above. They knew it was going to create
  confusion, and didn't want users or font developers to change
  their fonts

- When it comes to ClearType, things are different. According
  to the presentation file named "Avalon Text" (google for it),
  ClearType uses intrisically monochrome bitmap glyphs that are
  later composited, then box filtered, then LCD filtered, etc...

  that's probably why it doesn't exhibit the overlap problem at
  all. It is something you can do with FreeType (it would take
  some rather simple changes to libXft), but there are also
  many chances that it would infringe on the numerous patents
  that MS has on the technology.

More on this later,

- David Turner
- The FreeType Project  (

> -----Message d'origine-----
> De : address@hidden
> [mailto:address@hidden la 
> part de Hanno
> Mueller
> Envoyé : jeudi 6 octobre 2005 18:13
> À : Anton Zemlyanov
> Cc : address@hidden
> Objet : Re: [ft] Oversized "O"
> Anton Zemlyanov schrieb:
> > You should probably know that TT fonts have special "fitting" or
> > "hinting" process that uses byte interpreter to improve the 
> quality of
> > small fonts. Unfortunately this works good for monochrome 
> fonts only 
> By email, you requested a screenshot from a Windows system and as I
> already wrote you there, it seems to me that Windows is not using
> monochrome rendering as you guessed, but  subpixel aliasing for this
> font size, as well:
> Windows:
> Linux/X:
> > (MS seems to never use anti-aliasing for small font sizes).
> So far, I was under the impression that the "Core Fonts" once freely
> distributed by MS were optimized for screen reading incl. 
> good aliasing
> for small font sizes.
> > I found that anti-aliasing is not very beautiful for small 
> font sizes
> True, aliased fonts do look a bit "off" in Windows. Freetype's
> subpixel-aliasing is looking much better to me than the one 
> used by Windows.
> But my main gripe is the hardware resolution. I wish there were
> higher-resolution desktop TFT displays than the standard 1280x1024
> displays one can buy these days. Some laptops already use 1600x1200
> displays and there, subpixel-aliasing looks really nice. The 
> higher the
> dpi resolution of the TFT, the more impressive the effect.
> Best regards,
> Hanno
> _______________________________________________
> Freetype mailing list
> address@hidden

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