Michael J Lahey

US Patent:

48931160, Jan 9, 1990

Filed:

Nov 16, 1987

Appl. No.:

7/120902

Inventors:

David L. Henderson - Marlboro MA
Brian K. Herbert - Colorado Springs CO
Michael D. Lahey - Colorado Springs CO
Jamey L. Robbins - Colorado Springs CO

Assignee:

NCR Corporation - Dayton OH

International Classification:

G09G 114

US Classification:

340747

Abstract:

An interface controller, situated between a graphics controller and a memory array in a color video display system operable in a read-modify-write mode, configured to detect a select transparency color in whole or in part and to respond by selectively changing the color binary data for the corresponding pixel in a frame buffer. In another aspect, the invention includes drawing modes impelmented by logically combining pixel color binary data in accordance with a defined truth table so as to allow the pixel color data representing a new image to interact in a defined manner based upon color with the data in a previously defined image. As implemented, the binary data in the frame buffer is acted upon in a read-modify-write sequence whereby the various logic operations analyze the source (foreground) pixel data, the destination (background) pixel data, in the context of control signals, to define the pixel color data written into the frame buffer as the color representation for that pixel position.