MEHRSTUFIGE HALBTONRASTERUNG MIT GRUPPIERTEN PUNKTEN UND LINIEN FÜR DEN ELEKTROGRAFISCHEN FARBDRUCK

A method is disclosed for rendering monochrome or coloured continuous tone images by a system having restricted continuous tone rendering capabilities, such as electrographic printers capable of printing more than two density levels on each addressable micro dot. A method for preferred halftone dot growth is described, starting from isolated dots arranged along base lines and auxiliary lines, evolving to high density lines along the base lines and approximating full continuous tone rendition for high density regions. Preferred arrangements for the orientation, spacing and absolute location of the base lines and auxiliary lines are disclosed and a method to generate preferred arrangements. A moire free combination of three halftone images is described for the reproduction of colour images. A method to select a restricted set of energy levels to obtain linear reflectance response is disclosed. Halftone cells are arranged in supercells to improve the density resolution of the system.