Image binarization apparatus and method

摘要

A binarization circuit comprises the function (S21 to S31) of comparing the density value of the target pixel with the density value of surrounding pixels in the vicinity, the function (S21 to S31) of judging whether or not the target pixel is isolated from the surrounding pixels, and the function (S32 to S36) of detecting the density values of the target pixels which makes the target pixels isolated by binarization process, the function (S32 to S36) of calculating out accumulated isolated pixels frequencies of each density value detected by the detecting function when the judging means and the detecting means finished each process of all the original image, and the function of determining a threshold value on the basis of the accumulated isolated pixels frequencies.