Browse Prior Art Database

Software Blinking for Raster Display Devices

IP.com Disclosure Number: IPCOM000043083D
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Gay, AC: AUTHOR [+3]

Abstract

Blinking lines, characters, etc., on a display device involves drawing (or re-drawing) of the objects when the 'blink-phase' is ON and not drawing (or deleting) the objects when the 'blink-phase' is OFF. Also, when the 'blink-phase' is OFF, objects must still be processed so that the current position, modal parameters, etc., will have been updated for subsequent objects which may not be blinking. On a directed-beam display, blinking is achieved by turning off the input to the cathode or grid of the CRT or by turning down the intensity, while drawing the line (moving the beam). On a raster display, an analogy to this would be to plot pels (picture elements) into the bit plane with a zero value intensity, for example. In raster display systems, lines and characters are generated as sequences of pels plotted into the bit planes.

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Software Blinking for Raster Display Devices

Blinking lines, characters, etc., on a display device involves drawing (or re-drawing) of the objects when the 'blink-phase' is ON and not drawing (or deleting) the objects when the 'blink-phase' is OFF. Also, when the 'blink-phase' is OFF, objects must still be processed so that the current position, modal parameters, etc., will have been updated for subsequent objects which may not be blinking. On a directed-beam display, blinking is achieved by turning off the input to the cathode or grid of the CRT or by turning down the intensity, while drawing the line (moving the beam). On a raster display, an analogy to this would be to plot pels (picture elements) into the bit plane with a zero value intensity, for example. In raster display systems, lines and characters are generated as sequences of pels plotted into the bit planes. Color/intensity is given by the binary value through the bit planes at each pel position. On simple raster displays this binary value is input directly to the CRT (via a video amp) to display one of a selected set of colors. On more sophisticated raster displays, the binary color/intensity value is used to index a video lookup table containing the actual colors to be presented to the CRT for display. This system allows 2n colors to be displayed at any one time from a 'palette' of 2m colors, where n is the number of bit planes and m is the number of bits per entry in the lookup table. To implement blinking on this system, an extra bit can be included in each lookup table entry to indicate this value should be blinked by hardware (e.g., by turning video ON and OFF). This has a problem, however. For each color to be displayed, there must be two entries: one for no blinking of the selected color and one for blinking of the color, for example, a picture containing red lines, some which blink and some which do not. The two-entry solution is expensive due to the use of ECL logic required to implement the lookup table. One software/microcode solution would be to test for the requirement to blink when drawing and, if blinking, to just perform the appropriate update of current position and any other parameters. For example: PROC: DRAW_LINE (X,Y) IF line-blinking AND blink-phase-OFF

THEN

DO;

MOVE (X,Y);

END;

ELSE

DO;

DRAW (X,Y);

END;

END DRAW_LINE; This article describes a better solution. Performance of line drawing and character drawing, etc., can be improved by removing the blink testing at each draw. Blink testing should be performed when 'attributes' (describing a set of objects to be drawn) are set prior to drawing. As a result of testing, one of a numb...