[ft] Rasterizer specifics

[jmanson]

Hello,

I am in the process of writing a rasterizer of quadratic and cubic splines,
and am trying to learn what the current state of the art is in drawing
shapes with anti-aliased spline boundaries. Do you know of any good
reference papers (preferably academic), or a document that gives an overview
of the rasterizer used in FreeType?

I also have a couple of specific questions about the FreeType rasterizer. I
noticed that the function Split_Conic subdivides Bezier splines into smaller
arcs. Does FreeType calculate coverage exactly (i.e. directly from the
spline), or are splines approximated by piecewise linear segments that are
calculated through Split_Conic? If line segments are used, is a metric used
to guarantee accuracy to within some tolerance (presumably to the number of
grey levels, but maybe curvature)? 

>From the description in
http://people.gnome.org/~mathieu/libart/internals.html (from
http://old.nabble.com/The-FreeType-rasterizer-to14715693.html#a14715693) it
appears that a running sum of coverages are calculated from line segments
along a scan line. Does this ever result in numerical inaccuracies where
small residuals bleed out of the glyph at the end of a scan line?

Thanks a lot.
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