Electronic halftone screening

Abstract

An electronic signal representing the density of pixels in a scanned line in an original image and containing pixels in whole number multiples of a single line of halftone screen partial dot values plus a predetermined extension parameter is electronically halftoned by comparing the pictorial signal with the single line of halftone screen partial dot values to form an electronic halftone image. An electronic screen function represented by the single line of halftone screen values, produces automatically a rotated halftone screen at a predetermined angle to the original electronic image when the number of pixels in the input, scanned line of the original document is set equal to a whole number multiple of the number of partial-dot values plus a predetermined extension parameter. Under these conditions, the scanned input is automatically halftone screened electronically into halftone cells approximating a parallelogram and having said predetermined angle. The single line of partial-dot values need only be circularly buffered through a comparator. No electronic indexing or shifting of partial-dot values is required.