Patent ID: 7813007

Claim:
A dot data processing method of generating data of dots to be formed on a printing medium, comprising the steps of: a decoding preparation step of preparing a decoding table for pixel groups, each of the pixel groups grouping together a plurality of pixels that constitute a unit of dot formation, the table containing output dot arrangements and code values in a number of identifiers assigned to the pixel groups, the output dot arrangements and code values being associated, the output dot arrangements representing the dot on-off states for the pixels in the pixel groups, the code values assuming a prescribed range of values; a code value receiving step of receiving code values derived as a result of encoding of image data representing an image with a prescribed number of tones, the encoding being performed for each pixel group as an encoding unit; a decoding step of acquiring the output dot arrangement based on the received code value and the identifier assigned to the pixel group, by means of lookup in the decoding table; and a dot data output step of outputting dot data which represents an arrangement of dots to be formed on a printing medium, in accordance with the acquired output dot arrangement, wherein the decoding table associates the code values and the output dot arrangements depending on arrangements of selected threshold values, the threshold values being associated with pixels contained in the pixel groups while sequentially changing extraction locations from a dither matrix having threshold values of different values allocated according to a prescribed characteristic, and wherein the dither matrix is a global dither matrix containing threshold values in greater number than a tone number of the image.