Re: [Devel] default stem width and height for autohinting

[David Turner]

Hi Werner,

Werner LEMBERG wrote:
> The function `ah_hinter_compute_widths' relies on the existence of
> glyph `o' in the font.  What about searching for alternative glyphs
> depending on the font?  Especially in non-latin fonts, using `o' is a
> bad idea, since there a lot of fonts (especially CJK ones) which have
> extremely ugly shapes for ASCII since it is never used.  Even worse,
> the typographic properties can differ enormously between such ASCII
> glyphs and the real glyphs the font is used for.  The same problem
> exists for computing blue zones in `ah_hinter_compute_blues'.
> 
> Perhaps it makes sense to derive different global autohinting
> properties depending on the character range.  For example, a
> hyphothetical Near East font contains glyphs for Hebrew, Arabic, and
> the latin script.  If a Hebrew glyph has to be rendered, global
> autohinting properties derived from Hebrew glyphs only should be used.
> The same holds for Arabic and latin glyphs.
> 
> It shouldn't be too difficult to implement that.  The `blue_chars' has
> to become two-dimensional in some way, and we have to define leading
> characters for the various Unicode ranges to derive default stem width
> and height values.  For CJK, to name an example, a typical glyph could
> be the character for `ten': `十'.
> 
> Has anybody already done some tests whether this really improves
> autohinting results?
> 
Well, actually firefly's patch more or less does something similar
to what you describe, and I'm modifying the auto-hinter to
script-specific globals to be computed. The hard part is getting
all these things to run fast.

Hence the recent patch, which speeds up both stem recognition and
charmap iteration :-)

Cheers,

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


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