1. An image processing apparatus comprising: an input unit for inputting image data of an image composed of a plurality of pixels, each having a color data; a storage unit for storing a first condition on absolute positions of pixels in the image and a second condition on positions of pixels relative to a target pixel; a binarization unit for binarizing the target pixel based upon a color data of the target pixel and that of at least one related pixel to the target pixel in the image to generate a binarized value, the at least one related pixel satisfying the first and second conditions stored in said storage unit; and a determination unit for determining whether or not the image has a specified pattern, based upon binarized values obtained by said binarization unit.