PATTERN DETECTION PROGRAM, PATTERN DETECTING METHOD, AND PATTERN DETECTOR

摘要

A pattern detector estimates a boundary value a from document images inputted. The boundary value a is a value for distinguishing between the pixel values forming characters, diagrams and watermark patterns in document images and the pixel values forming the backgrounds. The pattern detector creates an image of each gray scale level composed of pixel values equal to or less than the boundary value a for each document image, matches the created images with the same gray scale level, identifies the gray scale level at which an average value of the matching scores is a maximum value, cumulatively adds the images of the identified gray scale level, and extracts the region which is probably a watermark character (the region where the probability of an embedded watermark character is high) from the cumulatively added image.