EMPHASIS ERROR DIFFUSION METHOD FOR COLOR REPRODUCTION OR BLACK AND WHITE REPRODUCTION

摘要

PROBLEM TO BE SOLVED: To solve an expression problem of details against the use of a print device of low image resolution by mixing the 1st and 2nd intermediate threshold masks obtained by the error diffusion of the 1st and 2nd gray level patches to form a threshold mask. SOLUTION: A 1st gray level patch having a fixed fray level showing the value of an irrational number is defined, and the error of the 1st gray level patch is diffused to the fixed threshold to obtain a 1st intermediate threshold mask. Then a 2nd gray level patch having a fixed gray level showing the value of an irrational number is defined, and the error of the 2nd gray level patch is diffused to a threshold group of 1st intermediate threshold masks to obtain a 2nd intermediate threshold mask. These 1st and 2nd intermediate threshold masks are mixed together to form a threshold mask. Thus, an error diffusion part 130 selects a proper error diffusion matrix based on the gray level and diffuses the errors to the peripheral pixel groups stored in a gray scale image store part 110 via a comparator 120.