To actualize color dropout technology that completely removes a specified color while holding image information.

By a method for performing the color dropout on a digitized document, a computer 10 obtains color values from the digitized document for background and a color of interest to a user. Then the color values of the background and the color of interest are transformed into an identical gray scale value according to a color dropout function. Further, a gray scale value different from the identical gray scale value is obtained from the remaining portion of the image according to the color dropout function and the gray scale values obtained from the previous steps are thersholded to obtain a binary image that substantially eliminates color classification error which retains character integrity by a functional transformation that suppresses color fringe artifacts.