US Patent 7843599 Image processing method and image processing apparatus

For each combination of color material signals corresponding to an input image signal, a total color material use amount is calculated. On the other hand, on the basis of a predetermined target color, total color material use amounts are set which vary smoothly in accordance with a variation in the target color. Then, a determination is made as to which one of all the combinations of color material signals determined as described above corresponds to one of the set total color material use amounts which is the same as the total color material use amount corresponding to the input image signal. This combination is outputted to a printer as the optimum combination of color material signals corresponding to the input image signal.