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Compression Algorithm for Alphanumeric Character Generator

IP.com Disclosure Number: IPCOM000109818D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 3 page(s) / 76K

Publishing Venue

IBM

Related People

Matsuyama, T: AUTHOR [+2]

Abstract

This algorithm relates to a method of how to compress the font data of an alphanumeric character generator in an efficient manner.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 73% of the total text.

Compression Algorithm for Alphanumeric Character Generator

       This algorithm relates to a method of how to compress the
font data of an alphanumeric character generator in an efficient
manner.

      The font data on a display terminal is usually composed of a
set of the dot matrices.  As shown in Fig. 1, in order to display a
character on the screen, the character generator scans the font data
and copies the font pattern in the video RAM.

      Especially, in the case where the font data involves a variety
of fonts and type sizes, the font data set is stored in the memory in
a compressed form and is decompressed when it is copied in the video
RAM by the character generator, as shown in Fig. 2.  Recently, the
size of a dot matrix was increased as the resolution of the screen
was improved.  As a result, the font data occupied a large space in
memory even if it is compressed.

      The conventional ways which are commonly used for any data
(text, graphics, image, etc.) compression can be used for the
character generator.  However, they are not always efficient for the
font compression.

      The alphanumeric character fonts do not include all the
combinations of the horizontal dot patterns.  In other words, the
traditional and typical characters which are 12 dots wide do not
include 2-exp(12) patterns in the font data set.  In fact, only
2-exp(2) patterns are sufficient.

      The new algorithm is based on the above fact.  All the
combi...