Re: [Devel] Kerning problem with capitals

[Alexei Podtelezhnikov]

Werner,

Freetype FAQ states that Freetype doesn't do kerning/positioning,
period. That pretty much addresses all tha past and future compains
about glyph spacing. I disagree with this, people keep complaining, and 
we are having this discussion. This is because Freetype matured and is 
very good in glyph rendering. Users started noticing inadequate spacing 
issues. 

Phylosophically, I believe that Freetype is the place to deal with 
generic word rendering. This is because freetype deals with fonts, which 
may or may not contain kerning info. Freetype can also use autokerner 
(rsb_delta+lsb_delta) in conjunction with autohinter. I have to repaet, 
that because of autohinting, there must be auto adjustment in spacing.
Freetype simply knows what happens to glyphs and even can evaluate 
hinting quality. It's way too much postprocessing to be passed on to 
higher level applications for a simple word rendering. 

Autohinter, which is probably the most widely used part of freetype, 
just doesn't make sense without autokerner.

Thanks,
Alexei 


On Thu, 9 Dec 2004, Werner LEMBERG wrote:

> > > This only exists for FreeType's autohinter.  What we've discussed
> > > before is a problem with the native TrueType hinter which normally
> > > doesn't handle sub-pixel rendering...
> >
> > I was under impression that the spacing problem has nothing to do
> > with subpixel rendering.
> 
> Oops.  I meant sub-pixel position corrections.
> 
> > Are you saying that TT hinter won't be able to detect these
> > distortions in terms or rsb_delta + lsb_delta?
> 
> Of course it does, but it doesn't expose this data to the
> application.
> 
> > I thought that rsb_delta and lsb_delta are of not much use
> > separately, while their sum actually means the spacing distortion,
> > which is easy to correct by removing or adding just one pixel.  Why
> > TT hinter doesn see it?
> 
> The concept of rsb_delta and lsb_delta is specific to FreeType's
> autohinter (it is an invention of David Chester).  It simply doesn't
> exist for TrueType, and it shouldn't be necessary at all for well
> hinted fonts.  The very idea of TrueType's hinting instructions is to
> have full control over all points.  In the specific case we've
> discussed in previous mails it is the kerning between `R' and `e'
> which must be handled more sensible.
> 
> 
>     Werner
>