Method of establishing halftone dot thresholds, apparatus for generating binary data, and image film/plate-making system

摘要

A supercell is divided into halftone dot cells each with a highlight point at center and halftone dot cells each with a shadow point at center. Thresholds 0, 1, 2, 3, . . . assigned to pixels in the halftone dot cells each with a highlight point at center and thresholds N, N-1, N-2, N- 3, . . . assigned to pixels in the halftone dot cells each with a shadow point at center are alternately determined, i.e., determined in the order of 0→N→1→N-1→, . . . → 3→N-3. When the density of an original image is high, the number of blackened pixels in the halftone dot cells each with a highlight point at center and the number of blank pixels in the halftone dot cells each with a shadow point at center are equalized to each other, thus preventing moire stripes from being produced which would otherwise be caused by a periodic change in the number of blackened pixels in the halftone dot cells.