Processor controlled photocomposition system

Abstract

A photocomposition system operating under microprocessor control to load, and alternatively display, character data from two respective bit maps. The data is assembled in the bit maps as a series of vertically adjacent video words generated from font data stored as a series of character boundary points and loaded into the bit maps in a controlled fashion to avoid destructive interference with image data already stored in the bit maps. Data in the bit maps can be displayed either on a CRT or via a laser printer or photocomposition system. System memory includes a plurality of fonts of data in which the characters are segmented into short segments and the boundary points thereof digitally recorded. From the recorded points, a curve fit of an arc section is used to define the complete character boundary for each segment and video data words are generated to indicate the boundaries on the vertical segments of the character defined by the arc sections fit to the recorded points. This video data is then applied to an image processor. While one bit map is used to generate display information, the other is loaded with each incoming video data word by cycling bit map data through an arithmetic logic unit controlled by the image controller to prevent newly inserted data from destructive interference with data already assembled in the bit map.