Re: [ft-devel] CFF hinting (was gamma correction and FreeType)

[Dave Arnold]

Hi Antti,

I don't know of any efforts to convert TT hints directly to CFF hints. The 
choice seems to be to throw away the TT hints and generate new CFF hints. You 
can easily experiment with the FreeType autohinter. I recommend the LIGHT mode. 
I think the autohinter is pretty good, and has the advantage of being built in 
to FreeType. It does not have stem darkening, however.

Adobe has used its own autohinter to do what you suggest, converting TT to CFF. 
This is used for embedding DefineFont4 fonts in Flash documents (DefineFont4 
fonts must be CFF). My experience is that the rendering results were frequently 
better than the original TT. Unfortunately, the Adobe autohinter is not open 
source and is better suited to offline usage (i.e., convert at authoring time, 
not at client viewing time).

Thanks.

-Dave


On 11/12/2013 10:52 PM, Antti Lankila wrote:
> Dave Arnold <address@hidden> kirjoitti 11.11.2013 kello 23.35:
>
> > Nothing stupid that I can see :-) .
> >
> > FreeType 2.5 made the new Adobe CFF rasterizer the default hinting engine for 
> > CFF. You can, at run time, select the autohint engine as an alternative.
> I found a couple of CFF fonts and played with them over the weekend. It seems 
> like the results with CFF hinting and stem darkening were actually really 
> good-looking at all sizes.
>
> However, TTF fonts get hinted in the old way, using either its bytecode or 
> autohinter. The bytecode may be designed for the aliased Windows rasterizer in 
> mind, which produces various problems with freetype when its program is 
> executed, or the autohinter tends to work poorly sometimes depending on glyph, 
> size, etc. So either way, results with TTF have a chance of being poor.
>
> I’m, however, encouraged by the results with CFF (though I only tried a couple 
> of font files so far). Has it been studied if converting the outline definition 
> from TTF to CFF automatically is feasible in order to always use this new 
> hinting engine, or should we basically throw away TTF files entirely now?
>
> —
> Antti