RE: [Devel] Re: Type 1 rendering and Euler numbers

[Turner, David]

Hi,

> > "Type 1 fonts use a different (undocumented) rasterization algorithm
> > that first creates a continuous outline that has no drop-outs, but
> > that is approximately 1/2 pixel too wide all the way around.  It
> > then erodes this outline using Euler-number-preserving binary image
> > operations – which cannot introduce drop-outs."
> 
> It's the first time I hear this.  Very interesting.  Any more
> information?  Note that the rasterizer has set the dropout mode
> hardwired to 2, regardless what the (TrueType) fonts asks for.  A
> longer time ago I asked for the reason, but I got no answer.  You
> might do some experiments and change it.
> 

Oops, I should have answered this one ! It's simply that experimentation
has shown that if you respect the drop-out mode according to the spec,
some TrueType fonts will not render correctly at small sizes.

But you should be able to see that by yourself, just uncomment the offending
line in ftraster.c, and you should be set.

> > 3. Would it help to turn on auto-hinting for Type 1 fonts? (Of
> > course I'll try this myself, but any other experiences are welcome).
> 
> Currently the auto-hinter produces better results than the Type 1
> hinter, I think.
> 
It depends, sometimes the Type 1 hinter is better at monochrome rendering.

Hope this helps,

- David Turner
- The FreeType Project  (www.freetype.org)

> 
>     Werner
> 
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>