DITHER MATRIX CREATING DEVICE

A dither matrix creating device acquires a basic dither matrix and modifies the basic dither matrix to provide a modified dither matrix including a plurality of sets of threshold value. Each threshold value set includes N threshold values (N≧2. An image processing device can perform both dither method and error diffusion method for converting an input image into an output image. Each pixel of the output image has an (N+1)-level output value. The modifying unit modifies the basic dither matrix by adjusting at least one of N threshold values such that the image processing device can produce a first output image by using the modified dither matrix according to the dither method. The first output image is more similar to an output image produced based on the input image according to the error diffusion method than an output image to be produced by using the basic dither matrix.