Digital rastering method of halftone image with raster having arbitrary raster width and raster angle

摘要

In a method for digital rastering of a half-tone image with rasters having arbitrary screen widths and screen angles, the rastering occurs by reading out a threshold matrix and comparing the thresholds that are read out to the color values of the half-tone image. For that purpose, a threshold matrix is employed wherein the thresholds represent one or more raster dots of a raster arranged at an angle, the desired screen width and the desired angle being approximated therewith. During the readout of the thresholds, an error between the desired raster and the raster approximated by the threshold matrix is calculated, and the error is compensated by a correction of the readout address for the threshold matrix as soon as the error exceeds a predetermined limit value. Alternatively, stored bit patterns can be employed instead of the threshold matrix, these having been acquired by comparing the tonal values to be reproduced to a threshold matrix.