Patent ID: 8730520

Claim:
An image processing method, comprising the steps of: converting input image data to ink color data corresponding to each amount of a plurality of colors of inks used for printing, the plurality of colors of inks including at least a first achromatic ink, a second achromatic ink having a higher printing density and a lower resin density than the first achromatic ink, and a third achromatic ink having a higher printing density than the first and second achromatic inks and a lower resin density than the first achromatic ink; and generating printing data for the first, second and third achromatic inks based on the ink color data, the printing data being used for printing by causing a printing head to scan a common image area in a printing medium a plurality of times, the printing head ejecting the plurality of colors of inks, wherein the converting step comprises converting the input image data to ink color data for the first, second and third achromatic inks so that the first achromatic ink is used with respect to a value of the input image data indicating achromatic color, the value being greater than a lower limit in a range where the third achromatic ink is used; and the generating step comprises generating the printing data for the first, second and third achromatic inks so as to (a) make a printing duty for the first achromatic ink during first half of the plurality of scans higher than a printing duty for the first achromatic ink during the latter half of the plurality of scans, and (b) make printing duties for the second and third achromatic inks during the latter half of the scans higher than in the first half of the scans, respectively.