Patent ID: 8023151

Claim:
An image processing method of 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 multiple sizes of dot formation on each of the print pixels to be formed on a print medium, the method comprising: preparing a first conversion table containing first correspondence relationships of pixel group tone values representing tone values of the pixel groups and multi-value quantization result values assuming a prescribed range of values, the first correspondence relationships being prepared for each of the pixel groups; preparing a second conversion table containing second correspondence relationships of output dot arrangements indicative of dot states for each pixel in the pixel groups and the multi-value quantization result values, the second correspondence relationships being prepared for each of the pixel groups; determining the pixel group tone value in response to the input tone value corresponding to the pixel group, among the image data; converting the determined pixel group tone value into the multi-value quantization result values for each of the pixel groups, by referring to the first conversion table; transforming the acquired multi-value quantization result 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, wherein the first correspondence relationships and the second correspondence relationships are configured to make a state of dot formation close to a predetermined characteristic over a whole range of the input tone values, wherein dot positions of at least part of the output dot arrangements are changed within each pixel group to make the state of dot formation closer to the predetermined characteristic with regard to each of partial ranges corresponding to each of total dot numbers of dots, the total dot numbers of dots being a sum of numbers of the multiple sizes of dots to be formed on the print medium, and wherein each of the operations of the image processing method is executed by a processor.