Color image halftoning with the dot overlap printer model

Color printers usually have only four inks (Cyan, Magenta, Yellow, and Black). They can not represent all colors of a color image. Traditional error-diffusion algorithm is proposed for solving this problem. In general, error-diffusion produces better halftoned images. Unfortunately, it also produces some artifacts, i.e. unstable phenomenon and smeared edges. These situations are much worse when dot overlap is included. We use a series of methods to improve the quality of halftoned color images displayed by printers with dot overlap. First, we show that the traditional error-diffusion algorithm may become stable if a proper formula is used to determine the color difference and propose a stable error-diffusion algorithm that does not consider the dot overlap. Then, we modify this error-diffusion algorithm as a new one which includes dot overlap. We also present a dot-size estimation method for this algorithm. Finally, the edge enhancement function is added into our error-diffusion algorithm Halftoning a color image by our proposed error-diffusion algorithm with edge enhancement has the following characteristics: the unstable phenomenon does not exit; the color-error caused by dot overlap is corrected and the smeared edges are sharpened.