Abstract: The image processing device of this invention processes an input document and performs a separation function which separates the text area and the image area from the input document. The image processing device first determines and coarsely separates the text area and the image area, then corrects the image quality. Then, the corrected image is finely separated into text area and image area, and corrected again. Logic calculation may be performed on the corrected images to further correct the image quality.

Abstract: Density data produced by an image reading unit is input to a surface density detection unit, which detects a surface density by averaging density data of pixels within a predetermined density range. A period setting unit sets a period of sampling density data of pixels to be used for calculation of the surface density. A surface reference density generation unit generates a surface reference density by adding an offset to the detected surface density. A surface color elimination unit corrects density data of a pixel lower than the surface reference density to the white level to eliminate a surface color.