Browse Prior Art Database

Graphic Data Reduction

IP.com Disclosure Number: IPCOM000078822D
Original Publication Date: 1973-Mar-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 73K

Publishing Venue

IBM

Related People

Lentz, JL: AUTHOR

Abstract

A right-angle polygon containing any number of exclusion right-angle polygons, is divided into rectangles prior to being printed by a computer driven graphic output device.

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At least one non-text object (such as an image or picture) has been suppressed.
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Graphic Data Reduction

A right-angle polygon containing any number of exclusion right-angle polygons, is divided into rectangles prior to being printed by a computer driven graphic output device.

A right-angle polygon is defined as any geometric two-dimensional figure having an even number of sides that always join at right angles. As illustrated in Fig. 1, right-angle polygon 1 comprises an outside polygon 2, all sides of which enclose all sides of an exclusion area or inside polygon 3. The X, Y coordinates of each vertex a-j of polygon 2 and each vertex K-P of polygon 3 are known and are specified in unbroken perimeter trace order, first for each vertex of polygon 2, then for each vertex of polygon 3. In each case, the coordinate specifications commence with the upper left-hand corner of the particular polygon, moving clockwise in a series of straight horizontal or vertical lines.

The output device, not shown, is assumed to be one in which the medium moves vertically from a supply spool to a take-up spool, and the printhead passes horizontally over the medium. Data fed to the device controls vertical motion of the medium and sets commands for printing a horizontal line of data. One vertical setting of the medium may contain one or more horizontal lines of data.

For the polygon illustrated, the coordinate input would be as follows:

(Image Omitted)

Beginning with the vertex in the upper left corner (X(a)Y(a)) of outside polygon 2, a Y-Change Table (Fig. 2) is created with each entry containing three items: Y; X BEGIN (the leftmost X), and X END (the rightmost X). Y(a) and Y(K) should not be included twice. Continue adding to this table until all polygons have been defined.

The entries on the Y-Change Table are not sorted in ascending Y sequence, producing the Table of Fig. 3.

An X-Tab Table is then generated. This table holds any number of pairs of X's for a given Y where the printhead starts and stops as it horizontally moves across the medium, analogous to tab settings on a typewriter. This X-Tab Table is developed as follows:

Beginning with the first entry Y(1) in Y-Change Taige (FIG. 3), insert X(a) and X(b) as the first pair of X's in the X-Tab Table.

(Image Omitted)

Since the next Y entry in the Y-Change Table is greater than the Y entry currently being examined, the program will process rectangle X(a), Y(1), Y(b), Y(2) (see Fig. 4)....