| 摘要 |
PROBLEM TO BE SOLVED: To determine whether each pixel is an edge pixel other than a thin-line edge pixel with less calculation quantity.SOLUTION: An edge determination part calculates, for a first processing area 65 where five pixels in a main scanning direction and three pixels in a sub-scanning direction are arranged in matrix with each of pixels 61 of averaged image data as its center, an edge determination value by use of a Sobel filter while multiplying an image density value of each pixel 61 located the closest to the outside in the main scanning direction with the center pixel 61a as its center by the image density value of the pixel 61 inwardly adjacent to the above pixel 61 in the main scanning direction. The edge determination part determines, when the edge determination value exceeds a first threshold, the center pixel 61a as a first edge pixel. The first threshold is equal to or more than the edge determination value in the first processing area 65 when the edge pixel of a thin-line pixel group is the center pixel 61a. |
