A Visual Model-based Halftone Pattern Design Algorithm

A genetic algorithm approach to the design of dither matrices used in the dispersed-dot digital halftoning method is described. Digital halftoning techniques are used to render continuoustone images on high resolution binary display devices. The dispersed-dot methods are an important class of digital halftoning techniques that map gray levels in an image into specific binary patterns. The design of such patterns to reduce visible artifacts is important so as to render the image with higher fidelity. A design approach based on shaping the spectrum of the dithering signal according to a model of the human visual system is presented. The design process is formulated as an optimization problem, which is solved by a genetic algorithm. Theoretical upper bounds to the performance are derived and the genetic algorithm generally finds solutions that are within 90% of the upper bounds. The dither matrices that are found by the new algorithm are used to render a number of example images.