Re: [Freetype-devel] Re: GSOC - Distance Fields

[Alexei Podtelezhnikov]

Hi Anuj,

> I have mostly completed the bitmap to SDF renderer (bsdf), there
> are only a few things remaining such as support for all pixel
> modes (currently it only work with FT_PIXEL_MODE_GRAY),

Only FT_PIXEL_MODE_MONO is necessary to add. I do not understand how
LCD or BGRA can be used for SDF; GRAY2 and GRAY4 are defunct.

> After that I have not decided what to do. I have a few things in mind (adding
> floating point support, removing overlaps [skip]

If I understand correctly, overlaps cause unexpected discontinuity in
SDF, which otherwise should not have any. I doubt that detecting and
removing contour overlaps is productive. I would rather deal with the
discontinuity directly. Perhaps there is a clever way to ignore
smaller distances that unexpectedly have an opposite sign. The
distance cannot change by more than the grid size. If it does, ignore
the offending value.

> CascadiaCode.ttf

Oh those variable fonts with overlaps...  When you read
https://docs.microsoft.com/en-us/typography/opentype/spec/glyf#simpleGlyphFlags
on OVERLAP_SIMPLE, there is a glimmer of hope: "either set this flag
in the derived glyph data, or else should merge contours to remove
overlap". So the flag is basically required in static fonts. I hope it
will be required in variable fonts too in the next version of specs.

Alexei