Digital Halftoning

This paper presents a new method of designing a dither matrix based on simulated annealing. An obtained dither matrix (halftone screen/mask) is appropriate for press printing. Because of several physical reasons, halftoning for press printing is more difficult than halftoning for electronic displays, or ink-jet printers. Even if stochastic dispersed-dot screening (so-called FM-screening) is one of the best solutions for halftoning, that is not appropriate for press printing. On the other hand, classical periodic clustered-dot screening (so-called AM-screening) is more important and is widely used even now. We recognize unfavorable quality of AM-screening, but we can not ignore its productive stability in printing section. The proposed halftone dither matrix has aperiodic clustered-dot pattern, and the size of cluster can be controlled by a weighting parameter of a cost function. We will obtain a dither matrix which consists of clustered-dots. Some characteristics of the design algorithm and halftoned images are investigated in detail. As a result, the fact that the obtained dither matrix is superior to AM-screen and comparable to FM-screen in visual quality, and the matrix is comparable to AM-screen and superior to FM-screen in press printability is confirmed. Application to an artistic screen and a blue-noise mask are also presented.