Abstract
This paper proposes a thresholding technique to extract characters from the background in a gray-scaled image with shading or highlights. The method can set a threshold automatically without any external parameters. The method uses the gray-levels of the plane-edge pixels that are located on the both sides of the general edge pixels. Because these plane-edge pixels are located near the gray-scaled planes compared with the general edge pixels, the gray-levels of the plane-edge pixels are supposed to be stable to the change of the position and the pose of an object to be extracted. The threshold is obtained from the averaged gray-levels of the plane-edge pixels with the maximum frequency of the plane-edge strength. The experimental results show that the characters were extracted clearly in the binary image by the proposed method in comparison with in the binary image by the discriminatory analysis method.
