Patent ID: 7760400

Claim:
An image processor, comprising: an input data corrector that corrects image data of a target pixel by giving a weight to error values in the neighborhood of the target pixel and adding weighted error values to a tone value of the target pixel; an output tone value determining unit that determines an output tone data of the target pixel based on corrected image data, and based on a threshold corresponding to a position of the target pixel; and an error value calculator that calculates a difference between the output tone data and the corrected image data as an error value, wherein the output tone value determining unit sets the threshold corresponding to the position of the target pixel to be within a numerical threshold range determined by a process that includes obtaining corrected image data when an output dot pattern output as an output tone value is in a steady state, and determining the numerical threshold range from the obtained corrected image data, wherein, in the steady state, a same output dot pattern is stably generated repeatedly as a result of repeated tone processing of a solid image having a certain input tone value, wherein the process of obtaining corrected image data is repeated for a plurality of different output dot patterns.