Patent ID: 6912068

Claim:
An image processor comprising: a multilevel error diffusion processing unit comprising: a quantizing unit that quantizes successively input pixel data based on output values distributed at predetermined tone differences; a quantization error detecting unit that detects an error of quantization of the pixel data; a peripheral error calculating unit that integrates the error of quantization of the pixel data detected by said quantization error detecting unit with respect to an error of quantization of peripheral pixel data; and an error superimposing unit that feedback-adds an integration error calculated by said peripheral error calculating unit to pixel data input next; a random noise generating unit that generates random noise in accordance with a tone level of the input pixel data; and a noise superimposing unit that superimposes random noise generated by said random noise generating unit on the pixel data before multilevel error diffusion processing is performed on the pixel data by said multilevel error diffusion processing unit, wherein said quantizing unit quantizes the pixel data based on a plurality of reference levels so that tone reproduction data output to an outside has at least two tone levels, wherein said reference levels are set so that a tone width of a plurality of areas divided based on the reference levels increases with the tone level and is narrow in a highlighted area where the tone level is highest.