AREA SEPARATING APPARATUS, IMAGE PROCESSING APPARATUS EMPLOYING THE SAME, AND AREA SEPARATING METHOD

An area separating apparatus for judging whether or not each object pixel belongs to a photograph image area in an image. The apparatus includes: an average value calculating circuit for calculating an average value of image data of pixels in an image block containing the object pixel; a photograph image area judgment threshold generating circuit for generating a photograph image area judgment threshold in accordance with the average value; a density difference summing circuit for determining differences in image data between respective adjacent pairs of pixels in the image block and calculating a sum of the image data differences for all the pixels in the image block; and a judgment circuit which judges that the object pixel belongs to the photograph image area if the sum of the image data differences is smaller than the photograph image area judgment threshold, and judges that the object pixel does not belong to the photograph image area if the sum of the image data differences is not smaller than the photograph image area judgment threshold.