FORMATION OF THRESHOLD MATRIX AND METHOD AND DEVICE FOR HALFTONING IMAGE

摘要

PURPOSE: To prevent the generation of undesirable dot patterns in FM screening. CONSTITUTION: Plural kinds of basic tiles of 2×2 dot sizes are used at the time of determining the threshold in an M1×M2 threshold matrix and are arranged within the M1×M2 threshold matrix region by prohibiting the basic tiles from the prescribed prohibiton arrangement with each other, by which 50% dot patterns or respectively 50% area raters of black dot and white dots are determined. A 0 and 1 as the values of the pair bit in the uppermost position of the digital data indicating the threshold are allotted to the two black dots in the respective basic tiles and a 2 and 3 are allotted as the value of the pair bit of the uppermost position to the positions of the two white dots. Different values of 0 to 3 are allotted to the divided four regions while the M1×M2 threshold matrix region is successively guadrisected as the value of the other pair bit of the digital datas showed the threshold, by which the threshold is determined.