DIGITAL HALFTONING WITH DOTS REPRESENTING A SPIRAL

摘要

A halftone raster image, suitable for rendering a continuous-tone image, which comprises a plurality of dots, arranged according a screen ruling and screen angle. Said dots comprise (i) image pixels arranged as a first arc or as a plurality of arcs which together represent a first spiral, and (ii) non-image pixels arranged as a second arc or as a plurality of arcs which together represent a second spiral. Small displacements of the feed point of said dots away from the theoretical centre of a halftone dot, defined by said screen ruling and screen angle, enable a higher image quality and less patterns in said halftone raster image.