Patent ID: 8693057

Claim:
A non-transitory computer-readable medium stored with a program causing a computer to quantize a gray level indicating the depth of color of each pixel in an image, the quantization comprising: a pixel selecting process of sequentially selecting pixels to be quantized; a use rate determining process of determining a noise use rate indicating the degree to which a dither matrix noise which is noise designated by a predetermined dither matrix has an influence on the quantization and an error use rate indicating the degree to which an accumulated error obtained by accumulating a quantization error which is an error generated in the quantization on peripheral pixels has an influence on the quantization, in which the noise use rate and the error use rate corresponding to the corresponding pixel are determined depending on the gray levels of the pixels sequentially selected through the pixel selecting process; and a quantization executing process of performing the quantization on the gray levels of the pixels sequentially selected through the pixel selecting process, in which the quantization is performed using the dither matrix noise based on the noise use rate corresponding to the corresponding pixel and using the accumulated error based on the error use rate corresponding to the corresponding pixel.