In a halftone module, it is judged whether or not the value 'rate' for each pixel is greater than zero (0). In other words, it is judged whether or not the eight-bit input data Iin of each pixel is around a half of the relative density value for a small dot of a corresponding color. If the eight-bit input data Iin of the subject pixel is near to a half of the relative density value for a small dot, noise is added to the threshold values Ta, Tb, and Tc. The noise-added threshold values Ta', Tb', and Tc' are used in the comparing process.
Image processing device and image processing program for processing a plurality of color signals formed of a plurality of color components