Image processing apparatus and method for expanding color images based on block pixel and edge detection

摘要

A printer system amd method for printing a clear image. When black characters or characters printed in a black reverse are expanded, the contours thereof are printed in black only and the inside or the outside of the contours which are designated to be printed in black color are printed in the three colors such as magenta, cyan and yellow in half tone or in an pseudo-half tone as well as in black. Image data is expanded on a image memory 1 according to instructions from a computer 1. A black- color determining unit determines whether or not the expanded image data includes a black pixel and an edge extracting unit 105 extracts an edge pixel in the expanded image data. A selector selects a black color only for a black edge portion and selects other colors in a half tone or in a pseudo-half tone as well as in black for a black but non-edge portion. It outputs the image according to such selections to a color printer.