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Re: [ft-devel] Improved auto-hinter algorithm


From: Dave Crossland
Subject: Re: [ft-devel] Improved auto-hinter algorithm
Date: Sat, 12 Apr 2014 21:02:42 +0200

Good stuff! The A is much better

On 12 Apr 2014 19:54, "Werner LEMBERG" <address@hidden> wrote:

Folks,


I've just improved the recognition of strong points in the
auto-hinter.  From the ChangeLog file:

  [autofit] Redesign the recognition algorithm of strong points.

  In particular, local extrema without horizontal or vertical segments
  are better recognized:

    + A                + D
     \                /
      \              /
       \            /
        \          /
         \        + C
          \    /
         B +/

  If the distances AB and CD are large, point B wasn't previously
  detected as an extremum since the `ft_corner_is_flat' function
  `swallowed' BC regardless of its direction, tagging point B as weak.
  The next iteration started at B and made `ft_corner_is_flat' swallow
  point C, tagging it as weak also, et voilà.

  To improve that, another pass gets now performed before calling
  `ft_corner_is_flat' to improve the `topology' of an outline: A
  sequence of non-horizontal or non-vertical vectors that point into
  the same quadrant are handled as a single, large vector.

  Additionally, distances of near points are now accumulated, which
  makes the auto-hinter handle them as if they were prepended to the
  next non-near vector.

  This generally improves the auto-hinter's rendering results.

Please test!  Note that the same change has been applied to
ttfautohint also; attached are two images that demonstrate the
expected improvements for some fonts.


    Werner

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