Browse Prior Art Database

Colored Line Segment Generation

IP.com Disclosure Number: IPCOM000050853D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 75K

Publishing Venue

IBM

Related People

Koelsch, AC: AUTHOR [+2]

Abstract

So-called "character graphics" displays may employ a pattern generator having special "characters" which constitute portions of graphic images when presented in contiguity on the screen of a display. This article describes the use of bit arrays which act as masks, to determine individually the color of each dot or pel (picture element) on such a graphic character.

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Colored Line Segment Generation

So-called "character graphics" displays may employ a pattern generator having special "characters" which constitute portions of graphic images when presented in contiguity on the screen of a display. This article describes the use of bit arrays which act as masks, to determine individually the color of each dot or pel (picture element) on such a graphic character.

Cathode ray tube (CRT) display 10 may have a raster scan image 12 which is generated by cyclic operation of a refresh memory 14. By addressing a store 16 in synchronism with the raster scan 12 operation of tube 10, refresh memory 14 causes the desired dot pattern to issue from store 16 to operate the electron beam controls 18 of tube 10 to create the desired image on its screen.

Color graphics can be provided by the use of a multiple gun shadow mask CRT, together with stores 16R, 16G, and 16B to provide red, green and blue color information for the image on a dot by dot basis. For this purpose, the store includes mask stores 16R, 16C and 16B in addition to dot pattern store 16P.

An example of a color graphic display is shown on the screen of CRT 10 in Fig. 1. Let it be assumed that it is desired to present a red line 20, a blue line 22, and a yellow line 24. These lines are created by dot patterns in the raster 12, the dot patterns being in contiguous screen fields of "character" cells as is common in alphanumeric and some graphic displays. One such cell is shown at 26, enlarged to show detail. It will be seen that cell 26 includes portions of lines 20, 22 and 24, including the crossing point of 22 and 24.

Fig. 2 illustrates, schematically, the operations of the apparatus of Fig. 1. Character cell 26 is 9 dots wide and 16 dots high, as are all the other cells (not shown) into which raster 12 of the display screen is divided. Store 16P includes various cells for use in constructing the display, among them one having a bit configuration in accordance with the ge...