Patent ID: 7619778
Filing Date: 2009-11-17
Classification: H04N

Abstract:
1. A method of generating a threshold matrix for producing each of color separations, the threshold matrix converting a continuous-tone image subjected to color separation into a dot pattern for each of the color separations, a color image being reproduced by overlaying the dot patterns, each of the dot patterns being a binary image in which no screen ruling or screen angle is defined, the method comprising the steps of: determining a pattern frequency at a predetermined dot percentage of an intermediate tone; and filtering a white noise pattern with a bandpass filter having a different characteristic for each of the color separations, digitizing a filtered pattern for obtaining a binary pattern, and determining a dot candidate position for placing a dot in a dot pattern based on the obtained binary pattern to obtain an array of the threshold, the bandpass filter having a main frequency of a bandpass characteristic that is substantially same as the pattern frequency for all angles, intensity distribution of the bandpass characteristic being modulated based on angles, and the intensity distribution being varied based on each of the color separations, wherein peaks of the intensity distributions of the bandpass characteristic for angles do not overlap each other among the color separations.