METHOD FOR SELECTING THRESHOLD OF BINARIZATION OF DIGITAL IMAGE

摘要

PROBLEM TO BE SOLVED: To provide a method for selecting threshold of binarization of a digital image by which the optimum threshold for the process of binarization for cutting down a background corresponding to a blank area of a document and a background corresponding to colors of a device itself from the digital image, and to provide a recording medium on which a program for selection of threshold of binarization is recorded. SOLUTION: The frequency distribution of luminance of the digital image is found and the necessity of decision for selection of the threshold corresponding to colors in the blank area of the document is discriminated by discriminating if Y/X is larger than 0.4 or not when the accumulated frequency in a first section where the luminance is 0-200 is X and the accumulated frequency in a second section where the luminance is 160-200 is Y. If Y/X is larger than 0.4, an optimum threshold for process of binarization for cutting down the background corresponding to the blank area of the document and the background corresponding to colors of the device itself from the digital image can be selected by selecting the value obtained by subtracting a specified value from the most frequent value in the second section as the threshold of binarization.