Image processing apparatus and method, dither mask set, and image recording apparatus

An image processing method for generating dot data indicating a disposition pattern of dots for each color for recording an image on a recording medium, while relatively moving a recording head having a nozzle row in which a plurality of nozzles that jet, for each of a plurality of colors of ink, each ink are arranged in a sub scan direction, in a main scan direction perpendicular to the sub scan direction and the sub scan direction with respect to the recording medium, comprising:

• a halftone processing step of performing halftone processing with respect to image data of a first color among the plurality of colors, in a range of at least a part of a recording duty, using a dither mask that realizes a first nozzle jetting rate in which a nozzle jetting rate of an end part nozzle located at each of both end parts of the nozzle row is suppressed to be smaller than a nozzle jetting rate of a central nozzle located at a central part of the nozzle row, and performing halftone processing with respect to image data of a second color different from the first color among the plurality of colors, in the range of the recording duty, using a dither mask that realizes a second nozzle jetting rate having smaller difference between the nozzle jetting rate of the end part nozzle and the nozzle jetting rate of the central nozzle than that in the first nozzle jetting rate.

A dither mask set that is used for halftone processing for generating dot data indicating a disposition pattern of dots for each color for recording an image on a recording medium, while relatively moving a recording head having a nozzle row in which a plurality of nozzles that jet, for each of a plurality of colors of ink, each ink are arranged in a sub scan direction, in a main scan direction perpendicular to the sub scan direction and the sub scan direction with respect to the recording medium, comprising:

• a dither mask that is used with respect to image data of a first color among the plurality of colors and realizes a first nozzle jetting rate in which a nozzle jetting rate of an end part nozzle located at each of both end parts of the nozzle row is suppressed to be smaller than a nozzle jetting rate of a central nozzle located at a central part of the nozzle row, in a range of at least a part of a recording duty;
• and
• a dither mask that is used with respect to image data of a second color different from the first color among the plurality of colors and realizes a second nozzle jetting rate having smaller difference between the nozzle jetting rate of the end part nozzle and the nozzle jetting rate of the central nozzle than that in the first nozzle jetting rate, in the range of the recording duty.