Subject: TTF to PS curve conversion (1/5)

From: "L.S.Ng" <[email-masked]>
Date: Sat, 28 May 1994 16:26:16 BST

True Type Font Curve Data to Postscript Curveto Data Conversion
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In certain applications, it is required to convert the True Type Font
Curve data to Postscript Curveto Data. For example, to print a Chinese
character defined in a Chinese TTF file to a Postscript printer.

The TTF Curve Data is suited Quadratic Bezier B-spline Approximation.
The number of data points (control points) may be 3 or more.

The Postscript Curveto Data is suited for Cubic Bezier B-spline
Approximation. The number of data points is exactly 4. In the case where
there are 4 data points, Cubic Bezier B-spline is the same as Cubic
Bezier Bernstein.

The procedure is:

1. Break the long Quadratic Bezier B-spline curve specified by the TTF
data into short Quadratic Bezier B-spline curve each having exactly 3
control points. In this case where there are 3 data points, Quadratic
Bezier B-spline is the same as Quadratic Bezier Bernstein.

2. Convert each short Quadratic Bezier B-spline curve into Cubic Bezier
B-spline curve specified by 4 data points. The result is the Postscript
curveto data.

The detailed description for each stage of the procedure is described
separately in the following 3 articles:

1. Algorithm for Splitting Long Bezier B-spline Curve
2. Evaluating B-spline function at whole number
3. Conversion of Quadratic Bezier curve to Cubic Bezier Curve