Patent US 5,477,346

A digital color copying machine improves the quality of an image of black characters by reproducing them with only black toner and prevents the edges of each black character from being colored with a color. The machine includes a monochromatic signal generator for generating a monochromatic signal in response to inputted plural color signals and an edge emphasizer for emphasizing edge components of the color signals with a predetermined edge emphasis amount. Either a digitizer for digitizing the monochromatic signal and outputting a binary signal of the monochromatic signal or a pseudo digitizer for generating a pseudo binary signal by steepening the contrast of the monochromatic signal is provided. A first area detector, second area detector, and third area detector are respectively provided for detecting first through third image areas. A first reproducer, second reproducer, and third reproducer are respectively provided for reproducing, in response to the binary signal, the color document image included in the first through third image areas detected by the first through third area detectors. A zoomer may be provided along with the pseudo digitizer, these zoomer performing a zooming process for the edge emphasis image signal with a predetermined zooming ratio such that the pseudo digitizer generates a pseudo binary signal by steepening the contrast of the monochromatic signal with a contrast conversion characteristic determined according to the zooming ratio.