Graphics processing apparatus having color expand operation for drawing

Abstract

A monochrome image becomes expanded into a color image for storage in a bit mapped color display memory. The color expand operation substitutes color data of one of two designated colors for the '1' or '0' monochrome data of a stored monochrome image. The first color code is substituted for all pixels of the monochrome image represented by a '1' and the second color code is substituted for all pixels of the monochrome image represented by a '0'. This color expanded image is then stored in the color display memory which controls the color picture shown to the user. This technique permits storage of commonly used images such as alphanumeric characters of various fonts or icons in a compressed form with one bit per pixel. These images are formed in color using the color expand operation at the time of drawing into the color display memory. Otherwise these images would need to be stored in multiple bit per pixel color form for all desired colors requiring considerable memory for redundant data. This color expanded image may then be combined with the color image stored in a selected part of the display memory and the combined image stored in that selected part of the display memory. Thus monochrome images may be expanded into color images and then combined with color images already in the display in a single operation.