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Dynamic font customization method through extracting/re-constructing subsets

IP.com Disclosure Number: IPCOM000013418D
Original Publication Date: 2000-Aug-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 3 page(s) / 60K

Publishing Venue

IBM

Abstract

Disclosed is a method to extract a variety of subsets from a parent font in such a way that a variety of mergers can be re-constructed later as desired from any combinations of the subsets. In this method, font metrics and typeface information except characterset information are preserved so that any subsets or mergers can be used as a replacement of their parent font. The original parent font can also be reproduced from the subsets if they are complemental each other.

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Dynamic font customization method through extracting/re-constructing subsets

Disclosed is a method to extract a variety of subsets from a parent font in such a way that a variety of mergers can be re-constructed later as desired from any combinations of the subsets. In this method, font metrics and typeface information except characterset information are preserved so that any subsets or mergers can be used as a replacement of their parent font. The original parent font can also be reproduced from the subsets if they are complemental each other.

This method is primarily designed as a simple characterset management function for applications that need to work with wide variety of charactersets on a small device. Unlike the other methods, this method actually removes unused glyph data in a font so that it keeps the font smaller, and also prevents the font from wasting limited system resources. By designing subsets carefully, the subsets can be downloadable through network and the method allows a small device to switch among several charactersets on the fly.

The method is also applicable to operating systems that need to support incremental installation for the fonts of large characterset, e.g., Unicode fonts.

Font file format

[1][2][3]A font file format is typically defined with the following set of records and tables.

font metrics and typeface information characterset information mapping table from code point to glyph index (cmap table) mapping table from glyph index to glyph data (index table) glyph data table (data table)

It is also equipped with a special glyph that is called default glyph to be used in the cmap table to address missing glyphs in a font file.

Extracting a subset

Extracting a subset means removing glyph data for unused glyphs in a font. The step-by-step operations are illustrated in Fig.1 below.

1

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font metrics information font metrics informationtypeface information

characterset charactersetinformation

4.update

3.remove

font metrics information typeface information

characterset information

code point to glyph index mapping table

glyph data table

glyph data to remove

code point

default glyph data

typeface information

information

mapping table

mapping table

glyph data table

default glyph data

code point to glyph index code point to glyph indexmapping table

glyph index to glyph data glyph index to glyph datamapping...