Image processing method and apparatus

Abstract

In accordance with the present invention, a quadratic differential values is first calculated, based on differences in the density data between an object pixel and respective peripheral pixels around the object pixel. The square value SS of the quadratic differential value S and the sum .SIGMA.SS obtained by adding up the square values SS of quadratic differential values for continuous five pixels are employed as determination values (step n1). The square sum .SIGMA.SS is compared with respective threshold values a, b and d, and the square value SS is compared with respective threshold values c, e and f (steps n2 to n6 and n8). Based on these comparison results, it is judged which image area among a character image area, gray-scale image area and dotted image area the object pixel belongs to. As for the image area judgement concerning the dotted image area, the final judgement that the object pixel belongs to the dotted image area is made only when nine continuous pixels including the object pixel are all judged to belong to the dotted image area. Since the square values SS and square sum .SIGMA.SS take only a positive value, the threshold values are set only in a positive range, and hence the image processing can be simplified. Further, by employing the square sum .SIGMA.SS, the states of the peripheral pixels can be taken into consideration for the image area judgement.