Patent ID: 7639399

Claim:
An image processing method of generating quantized output data having four-component output of cyan, magenta, yellow and black for an output device from image data having three-component input of cyan, magenta and yellow, the method comprising: using a processor to perform the steps of: inputting image data of a pixel of interest; generating input data by adding error data, calculated from color difference data of pixels around the pixel of interest, to the image data; extracting the high-order bit data from each of the three-component input of the generated input data; deciding the quantized output data of the pixel of interest and output density data of the pixel of interest, by referring to a multidimensional table based upon the extracted high-order bit data, wherein the multidimensional table stores a correspondence between the input data, the quantized output data and the output density data and wherein the output density data has the three-component input of cyan, magenta and yellow, and represents a density of an output image reproduced by the output device based upon the quantized output data; and calculating the color difference data of the pixel of interest by subtracting the decided output density data from the generated input data, wherein the quantized output data included in the multidimensional table is decided such that a cyan dot and a magenta dot are not simultaneously output by the output device in an area where a value of the cyan component and a value of the magenta component are low, and is decided so as to minimize the difference between the input data and the output density data in other areas.