An image processing method involves processing image data indicative of an image represented with a prescribed number of input tones by each of pixel groups composed of a plurality of print pixels, and generating dot data representing a status of dot formation on each of the print pixels to be formed on a print medium. The method includes preparing a first conversion table and a second conversion table, determining the pixel group tone value in response to the input tone value corresponding to the pixel group, converting the determined pixel group tone value into the code values for each of the pixel groups, by referring to the first conversion table, decoding the acquired code value into the output dot arrangement for each of the pixel groups, by referring to the second conversion table, and outputting the dot data in response to the output dot arrangement.