APPARATUS AND METHOD FOR PSEUDO GRAY SCALE CONVERSION

摘要

PROBLEM TO BE SOLVED: To make granularity inconspicuous by preventing generation of texture in pseudo gray scale conversion of a high quality multilevel halftone image. SOLUTION: A threshold value generating section 100 receives addresses X and Y for designating the least significant 5 bit data D of input pixel data and the position in three kinds of offset matrixes and delivers a threshold value Th+To corresponding to these input values to an error diffusing section 101. The error diffusing section 101 receives the least significant 5 bit data D of input pixel data and the threshold value Th+To and performs a well known error diffusion processing before outputting a carry value. An adding section 102 adds the carry value to the most significant 5 bit data U of input pixel data to produce 5 bit data U'. A gray scale converting section 103 outputs the most significant 4 bit of the 5 bit data U' as output pixel data.