Patent ID: 8498013

Claim:
A fluid ejection device comprising: a first nozzle row having nozzles configured and arranged to eject a fluid onto a medium with the nozzles being arranged in a prescribed direction, the first nozzle row being configured to form a first band image while facing a first location on the medium; a second nozzle row having nozzles configured and arranged to eject a fluid onto the medium with the nozzles being arranged in the prescribed direction, the second nozzle row being configured to form a second band image while facing a second location on the medium; a third nozzle row having nozzles configured and arranged to ejecting a fluid onto the medium, the nozzles being arranged in the prescribed direction, and the third nozzle row being configured to form a third band image while facing a third location on the medium; a storage portion configured to store a dither mask used in a halftoning process for converting input data composed of a plurality of arranged pixels into dot data representing dot on/off states, the dither mask having edge areas that are areas at both edge portions in the prescribed direction and a center area that is an area at a center portion in the prescribed direction, and having a plurality of arranged threshold values; and a control portion configured to form, based on the dot data, an image in which an edge portion lying to one side in the prescribed direction in the first band image overlaps an edge portion lying to the other side in the prescribed direction in the second band image, and an edge portion lying to one side in the prescribed direction in the second band image overlaps an edge portion lying to the other side in the prescribed direction in the third band image, associate the dither mask stored in the storage portion with the input data for forming the second band image, and carry out the halftoning process with the dither mask in which a number of the threshold values arranged in the prescribed direction is equal to a number of the pixels arranged in the prescribed direction in the input data for forming the second band image with a dot generation rate in the edge areas being lower than a dot generation rate in the center area, and carry out the halftoning process upon the center area and the edge area lying to the one side in the prescribed direction in the dither mask being associated with the input data for forming the center portion and the edge portion lying to the one side in the prescribed direction in the first band image, and upon the center area in the dither mask being associated with the input data for forming the edge portion lying to the other side in the prescribed direction in the first band image.