Resolution enhancement of half-toned black data transmitted with color data

Abstract

When black regions are adjacent to color regions, the adjacent black regions are encoded (rendered) at the resolution of the color regions (e.g., 300 dpi) even though the printer has the capability of printing black at a higher resolution (e.g., 600 dpi). To make full use of the 600 dpi resolution of the printer, the black pixels are separated from the color pixels. The 300 dpi resolution black pixel field is converted to a 600 dpi black image field. A window surrounding a selected group of (600 dpi) black/white target pixels is chosen. The pixels in the window are applied to a logic circuit having a plurality of logical conditions. As a result of the logic processing, values of each of the target pixels can be changed to a different pixel value to avoid jagged edges in the printed images, thereby providing a pseudo-600 dpi resolution for the target pixels. The logical operations are performed until all of the pixels have values determined by the logic circuit. The resulting processed pixel field provides a more satisfactory printed image. The window is selected so that the pixel fields can be represented by word-length data groups. Black pixels rendered at the higher resolution are generally unaffected by the logic circuit. Thus, black pixels are rendered at two resolutions but printed at the same resolution.