Image forming apparatus and computer program product

A computer program product comprising a non-transitory computer-readable medium including programmed instructions, wherein the instructions, when executed by a computer that transmits image data to an image forming apparatus including print heads that eject ink droplets of a plurality of coloring materials from nozzles thereof onto a recording sheet conveyed by a conveying unit, the print head for a first coloring material among the plurality of coloring materials being arranged such that the first coloring material is to be ejected later than other coloring materials on each of a forward stroke and a backward stroke in bi-directional printing, and the print heads for the other coloring materials being arranged in tandem in a main-scanning direction, cause the computer to execute:

• performing first color conversion of converting the image data received from the computer into first image data for the plurality of coloring materials for use by the print heads in printing in any one direction of the forward stroke and the backward stroke;
• performing second color conversion of converting a part of the first image data into second image data for the other coloring materials for use in printing in a direction opposite from the one direction, the part of the first image data being obtained by excluding image data for the first coloring material from the first image data;
• and
• switching between causing and not causing the second color conversion to be performed on the part of the first image data depending on which one of printing in the forward stroke and printing in the backward stroke is to be performed by the print heads.