Patent ID: 7327491

Claim:
An image processing apparatus which inputs and quantizes multivalued image data representing each color by plural bits into image data of a lesser number of bits, comprising: addition means for adding an error of each color that has occurred in previous quantization to the input multivalued image data of each color; and quantization means for inputting the M (M≧2) multivalued image data after the addition obtained by said addition means as M addresses and outputting the data after the quantization of the respective colors in accordance with the input M addresses, wherein said quantization means comprises a look-up table for storing the data after the quantization in an M-dimensional space accessed by the input M addresses, and wherein, in said M-dimensional space, the look-up table stores, with respect to the high-density area, the data after the quantization having no correlation among address values of the respective colors and stores, with respect to the highlight area, the data after the quantization having correlation among the address values of the respective colors, such that dots of one of the respective colors are arranged with appropriate distances from dots of another of the respective colors.