1. An image processing method for processing an image with a gray-level distribution of pixels, characterized in that it comprises the steps of: a) calculating a statistical distribution of the gray-level of the pixels of said image; b) detecting edge pixels in the image in accordance with an edge criterion corresponding with the statistical distribution of gray-level; c) dividing said image into a plurality of sub-images; d) determining a binarizing threshold for each of the sub-images in accordance with the gray-levels of the edge pixels detected in the same sub-image; e) binarizing each of the sub-image in accordance with the binarizing threshold determined for the same sub-image.