Patent ID: 7724395

Claim:
A dot arrangement determination method performed in a signal processing device for determining an arrangement pattern to create a pseudo gradation image when m dots (where m is a natural number) corresponding to a plurality of recording elements are arranged in a specific pixel area in the pseudo gradation image, the method comprising: a setting step of variably setting by utilizing a setting device, an arrangement pattern in which the m dots are arranged without overlapping at pixel positions in the specific pixel area; a first image evaluation value calculating step of calculating an image evaluation value of a halftone image formed by arranging the m dots in the specific pixel area in accordance with the arrangement pattern set in the setting step in a case assumed that there is no inability to form the m dots; a second image evaluation value calculating step of calculating an image evaluation value of a halftone image implemented according to the arrangement pattern set in the setting step in a case assumed that there is inability to form dots in an arbitrary pixel row in the specific pixel area without determining which recording element is defective; and a dot arrangement calculating step of determining the arrangement pattern with least image quality degradation for the inability to form the dots in the arbitrary pixel row in the specific pixel area by solving a combinational optimization problem by using an approximate solution method for the arrangement pattern using calculation results of the first and second image evaluation value calculating steps.