Patent ID: 8363279

Claim:
A method, performed by an image recording apparatus, for setting multiple tones in a halftone process upon recording an image using ink, the method comprising the steps of: (a) determining, by the image recording apparatus, for each of the multiple tones, a corresponding base dot pattern for the tone, the base dot pattern including plural dot areas, the plural dot areas including at least one non-discharged dot area between each pair of discharged dot areas along a horizontal direction, and including at least one non-discharged dot area between each pair of discharged dot areas along a vertical direction, each non-discharged dot area being a dot area for which the ink is not discharged as a dot, and each discharged dot area being a dot area for which the ink is discharged as a dot; (b) setting the multiple tones to respective base dot patterns, determined in (a), such that for each tone of the multiple tones, at least one non-discharged dot area is present between each pair of discharged dot areas along the horizontal direction and at least one non-discharged dot area is present between each pair of discharged dot areas along the vertical direction, in the base dot pattern set to the tone; (c) performing an error diffusion method to express halftones in the halftone process; (d) determining whether the ink is discharged as a dot on a preceding dot area, based on a threshold value; and (e) determining, in a case that it is determined in (d) that the ink is discharged as a dot on the preceding dot area, regardless of the threshold value, that the ink is not discharged as a dot on a current dot area.