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3. Conversion of TrueType outline fonts from bitmap data

3.1 Overview

The Asian and African fonts library (AA-Fonts, see chapter 2) was developed by the Institute of the Study of Languages and Cultures of Asia and Africa, Tokyo University of Foreign Studies by Professor Shuji Matsuhita, and is available for the academic use. The AP Font (Asia-Pacific Font) TrueType library is largely based on the conversion of glyphs in AA-Fonts under the cordination of AP Font Study Group (AP Font SG) with permission of the institute.

3.2 Conversion from Bitmap to Outline

Each character of AA-Fonts consist of attribute parameters and 96 x 96 dot matrix pattern, or bitmap data (see chapter 2). Figure 3-1 shows the bitmap pattern of a character in the Khmer Language.

[Figure 3-1: bitmap glyph]

The AP Font Library was constructed by the following programs which were originally created at National Taiwan University by Mr. Lin Yaw-Jen.

(1) [ttfstub] generate the stub (root) part of TrueType file.
(2) [aaf2bmp] extend the 1024 x 1024 bitmap data from AA-Fonts.
(3) [freeman] extract the freeman coded and the attribute parameters from (2)'s bitmap data.
(4) [vector] fit (3)'s freeman points to vectors. Each vector is a small line segment. The threshold parameter is the length of trace over the direct distance.
(5) [spline] fit (4)'s vector font as Q-splines. Each spline has a control. The threshold parameter is the average distance after regression.
(6) [toglyf] store (5)'s spline file as the glyph format that TrueType specification defined.
(7) [add] add (6)'s glyph and (2)'s attribute parameters to (1)'s TrueType file.
Figure 3-2 shows the outline pattern of same character as Figure 3-1.

[Figure 3-2: outline glyph]

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