Re: [ft-devel] GX support now working

[Dave Arnold]

Hi Werner,

On 6/8/2015 2:20 AM, Werner LEMBERG wrote:
> > Adobe rasterizers typically use even-odd at small sizes and non-zero
> > at larger sizes.
> Interesting.  What's the rationale for that?  And which ppem values
> are `small sizes'?  I would also like to know whether this is a
> general thing, independent of the font format (i.e., TrueType
> vs. PostScript outlines).
I've checked around at Adobe, and find that my memory is incorrect. The small 
sizes are non-zero and the large sizes are even-odd.

The threshold is 400 ppem. Below that size, a "center scan" algorithm is used. 
It is a newer algorithm than the original scan converter and produces better results. But 
it runs slower and takes more memory, so the original is still used at large sizes.

The TrueType rasterizer that Adobe licenses from Microsoft has its own scan 
converter.

Thanks.

-Dave