To realize a top-down type segmentation method that finds out a photographing area on the basis of entire pixel connectivity.

An area-based binary processing system applies adaptive threshold processing and image rendering to a gray scale image to generate 1st and 2nd binary images. The gray scale image is sub-sampled to obtain a low resolution image and a position of a photographing image is detected in the low resolution image. Furthermore, a rectangular photographing image is identified in the detected photographing image and a classification map to distinguish pixels of the rectangular photographing image from other pixels is produced. Then a final binary image can be formed from the 1st and 2nd binary images on the basis of the classification map.