A plurality of color data respectively undergo quantization processing, and a logical multiplication of the plurality of quantized color data is calculated. A product of the plurality of color data is calculated. A first low frequency component is extracted from the logical multiplication, and a second low frequency component is extracted from the product. The first low frequency component is subtracted from each of the plurality of color data, and the second low frequency component is added to the subtraction results to generate a plurality of corrected color data. The plurality of corrected color data respectively undergo the quantization processing.