[Devel] Type 1 rendering and Euler numbers

[Graham Asher]

Dear FreeTypers (if there are any of you out there - the mailing list has
gone rather quiet of late),

I've had some trouble with the quality of Adobe Type 1 fonts at low
resolutions (sample of cmr12.pfb at small ppem attached as a bitmap image
enlarged threefold: note dropout on top-right branch of 'x', for example).
Three questions:

1. Does anybody have a high-quality Type 1 font they can send me for
testing? I am using the Type 1 versions of Knuth's CMR fonts, made available
by the American Mathematic Society, and the fonts supplied with GhostScript.
I'm not sure if these are up to the quality of professional paid-for fonts.
Please don't break any license agreements when sending me anything .

2. Berthold Horn notes (‘Hinting’ of scalable outline fonts, TUGboat, Volume
18 (1997), No. 4) that the less powerful hinting system relies on a subtler
rasterizer:

"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."

FreeType uses a single rasterizer for all font types, so obviously cannot do
this - I think. Any comments?

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).

Best wishes,

Graham Asher

type1-example1.bmp
Description: Windows bitmap