Patent ID: 7782493

Claim:
A method of generating a threshold matrix which is compared with an original image of gray scale for each color component in creating a halftone dot image which represents said original image, said threshold matrix for said each color component being generated in a matrix area for said each color component corresponding to each of repeat areas which are set by dividing said original image into areas having the same size in creating said halftone dot image, said halftone dot image being recorded on a recording medium in an image recording apparatus, comprising the steps of: a1) arranging a plurality of first base points in a matrix area for a first color component in a random fashion at a predetermined density, said matrix area for said first color component being set in a memory; a2) generating a threshold matrix for said first color component by setting threshold values in said matrix area for said first color component so that dot-like halftone dot areas grow from said plurality of first base points in a halftone dot image in accordance with an increase in gray level of a first original image; b1) arranging a plurality of second base points in a matrix area for a second color component in a random fashion at a certain density higher than said predetermined density and lower than twice said predetermined density, said matrix area for said second color component being set in a memory; and b2) generating a threshold matrix for said second color component by setting threshold values in said matrix area for said second color component so that dot-like halftone dot areas grow from said plurality of second base points in a halftone dot image in accordance with an increase in gray level of a second original image, wherein said first color component is black and the size of each of said dot-like halftone dot areas for black is made larger than that for said second color component in the same gray level.