Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Graphic Compare for Digital Television Generator

IP.com Disclosure Number: IPCOM000078220D
Original Publication Date: 1972-Dec-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 3 page(s) / 33K

Publishing Venue

IBM

Related People

Cook, WC: AUTHOR

Abstract

Most digital television systems today employ some means of locating a particular point upon the display screen of the system. This is usually done with either a cursor which is manually operated at the control panel, or a light pen which is manually directed to the surface of the display screen. Often it is desirable to determine the relative proximity of this defined point, whether it be by cursor or by light pen, to the various symbols and vectors being displayed upon the screen. Present day systems usually involve complicated logic systems to perform this function, usually requiring excessive use of the central processing unit (CPU) for these calculations. For example, if the operator wishes to determine if the light pen is directed to a particular vector, the system must be capable of two different types of comparisons.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 3

Graphic Compare for Digital Television Generator

Most digital television systems today employ some means of locating a particular point upon the display screen of the system. This is usually done with either a cursor which is manually operated at the control panel, or a light pen which is manually directed to the surface of the display screen. Often it is desirable to determine the relative proximity of this defined point, whether it be by cursor or by light pen, to the various symbols and vectors being displayed upon the screen. Present day systems usually involve complicated logic systems to perform this function, usually requiring excessive use of the central processing unit (CPU) for these calculations. For example, if the operator wishes to determine if the light pen is directed to a particular vector, the system must be capable of two different types of comparisons. First, if the light pen is directly on the vector, the CPU which usually has a starting point X1, Y1 of a vector plus Delta X, Delta Y components, must calculate each point on the vector beginning with X1, Y1 and compare each point with the light-pen location, to determine if the light pen is on the vector line and where. This is a relatively time consuming process for the CPU, and if the light pen is not directly on the vector line no compare will result. When the light pen is not directly on the vector line, a second and much more complex comparison operation is necessary to determine the relative proximity of defined points on the vector line. The type of comparison usually employs a greater than less than calculation, which is not only time consuming but which requires a complex circuitry, thus increasing the expense of the system.

The above system performs the graphic compare in an inexpensive and relatively fast manner. During the compare mode, the CPU erases the contents of raster assembly store 10 and writes therein a pattern which cont...