1. An image processing device comprising: an image segmentation unit that divides an image information set into a plurality of image areas, the image information set forming a plurality of lines each constituted of colored pixels arrayed in a first direction, and the image information set expressing one or more gradations forming an image as a number of the colored pixels existing in a predetermined image area; an image area shift unit that shifts the predetermined image area among the plurality of image areas in a second direction different from the first direction, relative to an image area substantially contiguous to the predetermined image area; and a pixel replacement unit that replaces at least one the colored pixels forming part of each of the lines and existing within a predetermined distance range from the boundary, with at least one of the colored pixels intervening between the lines, if each interval between the lines on a boundary between the predetermined image area and the substantially contiguous image area in the image after shifting the predetermined image area by the image area shift unit is narrower than each interval between the lines on a boundary between the predetermined image area and the contiguous image area in the image before shifting the predetermined image area by the image area shift unit.