An image processing device includes storage units to store a first halftone pattern subjected to a halftone processing for a first color gradation value, a second halftone pattern subjected to a halftone processing for a second color gradation value, and a brush pattern. The device further includes shift units to shift each pattern read on the basis of a predetermined unit from each of storage units to a first direction toward a drawing start point on the horizontal line according to a drawing position on the horizontal line, further add each pattern to a second direction toward a drawing end point on the horizontal line, and output each on the basis of the predetermined unit. The device further includes a brush synthesizing unit to select, pixel by pixel, either the first halftone pattern or the second halftone pattern, according to the brush pattern.