Re: [ft-devel] a hidden gem: the autohint warper code

[Werner LEMBERG]

>>>> If the bottom line of the warped glyph is shifted away from a
>>>> bluezone, then the whole glyph should be shifted back a whole
>>>> 1?pixel back toward the bluezone after being warped.
>>> 
>>> This won't work.  If you shift one pixel back, all other optimized
>>> zones, would be at the wrong position.  Warping, as it is
>>> currently implemented, only works if the code has the absolute
>>> freedom to positions stems at any places.

Oops!  I've read `scaling' but you were talking about `shifting',
sorry.  Shifting is always in the range of a half pixel left or right.

> I assume when finding the best score, the shift and scale performed
> in the warper code are uniform over the whole glyph points.

Yes.

> After tiny scaled/shifted, the stems are then grid fit to pixels.

No.  The scaling/shifting process is essentially done *instead* of
grid fitting (with `grid fitting' I mean rounding of stems to the
grid).  Remember that warping works only in the `light' autohint mode
which doesn't apply hints to the x coordinates.

Warping and autohint grid fitting simply don't combine.


    Werner