A Multilevel Algorithm for High Quality Digital Halftoning

Abstract

For digital halftoning of photographs and screened dot pictures, it is advantageous for printers to have a capability for a few gray levels in output image than the conventional bilevel one.
A new multilevel CAPIX algorithm for high quality digital halftoning is developed by expanding the concept of the CAPIX (Correlative density assignment of adjacent pixels), which is widely used for high quality bilevel halftoning in the field of office equipment.
A 4-level CAPIX is simulated and evaluated by comparing it with the bilevel output. The 4-level CAPIX is shown to be very effective in improving the fineness and smoothness in gray level reproduction.