For each of the color components of an inputted continuous tone color image, densities of the pixels are successively compared with a threshold value, thereby converting the pixels into ON or OFF. A binary conversion error obtained during this conversion operation is distributed to neighboring pixels. A printing prohibiting matrix is previously set to determine several pixels to be compulsively turned OFF. The error diffusion conversion process is attained with using the printing prohibiting matrix, thereby reducing the number of turned ON pixels and limiting the amount of ink to be ejected.
Method of converting continuous tone color image into pseudo-halftone binary color image