Patent Document ID: 6014465
Application ID: 08913415
Patent Status: 1

Claim One:
1. A method for transforming a gray-level image which is divided into pixels, into a black-and-white image, comprising the steps of: dividing said gray-level image into a number of generally square and non-overlapping sub images that are mutually arranged to cover said gray-level image, each one of said sub images comprising more than one pixel; calculating, for each one of said sub images, a first maximum value and a first minimum value based on the gray-levels of the pixels in the sub image; calculating, for each one of said sub images, a threshold value by: determining a primary maximum value from the first maximum values of the sub image and a number of sub images that are adjacent the sub image; determining a primary minimum value from the first minimum values of the sub image and a number of sub images that are adjacent the sub image; and calculating a weighted average value of the primary maximum value and the primary minimum value as the threshold value; and transforming, for each one of said sub images, each pixel in the sub image to either a white or a black pixel depending upon whether the gray-level of the pixel exceeds the threshold value of the sub image or not.