RE: [Devel] outlines

[John Schuch - ID]

-----Original Message-----
From: Graham Asher [mailto:address@hidden
Sent: Wednesday, March 12, 2003 2:08 PM
To: address@hidden
Subject: RE: [Devel] outlines

<<<<<<
I have done a lot of reading as I am new to all of this, but I have yet to
find any real comprehensive information about
outlines. For example, each point in an outline has an associated tag, and
that tag has some meaning for the point. Are the
conic/cubic tag on/off the only important values for a tag?  And if this is
so, why are there more than 3 possible values for
tags as I have seen when reading font info from a font file? Also, if
somebody could point me in the direction of some good
information on how to construct outlines based on point info, I would
greatly appreciate it. So far it eludes me as to how to know
to jump to a point without drawing a line to it, for example.
>>>>>>

-Points are tagged as either on-curve, conic (quadratic) control point or 
-cubic control point.
Are these the only values that are meaningful? What I mean is, are some
points
tagged in such a way as to say, 'don't draw a line or curve to me.' For
example, drawing
an 'O' requires drawing to ovals. How does the outline info differentiate
between
the inner and outer oval? Does it?


-A straight line is drawn between two on-curve points. A conic Bezier spline
is
-defined by two on-curve points with a single conic control point between
-them. A cubic Bezier spline is defined by two on-curve points with two
cubic
-control points between them.

-There is a special case: if two conic control points are next to each other
-an on-curve point is assumed to exist half way between them, and is
-automatically inserted as the outline is rasterized.


-There is no special treatment for illegal sequences of cubic control
points.

Does this mean that illegal sequences are commonly found?

Hope this helps.

Graham Asher



_______________________________________________
Devel mailing list
address@hidden
http://www.freetype.org/mailman/listinfo/devel