Patent ID: 7653239

Claim:
An image processing method for processing each pixel data of an input image obtained by reading an original image while a line sensor moves, relative to the original image, in a sub-scanning direction perpendicular to a main scanning direction, the image processing method including: determining whether a target pixel is a pixel constituting a monotone increasing part or monotone decreasing part of a luminance value of the input image, on the basis of luminance data for the target pixel and only two neighboring pixels positioned on both sides of the target pixel in the sub-scanning direction, with a luminance change detection circuit; calculating new color difference data by employing an operational algorithm that is selected from among multiple operational algorithms, including first and second operational algorithms, based on whether the target pixel is determined to be a pixel constituting a monotone increasing part or monotone decreasing part of a luminance value of the input image, with a color difference data calculation circuit; and synthesizing the new color difference data obtained by the color difference data calculation circuit with the luminance data for the target pixel with a color space conversion circuit to acquire new image data corresponding to the target pixel; wherein the first operational algorithm is a calculation for employing a median filter to the color difference data of the target pixel and the neighboring pixel and for outputting color difference data as the new color difference data, and wherein the second operational algorithm is a calculation for employing a median filter to the color difference data of the target pixel and the neighboring pixel and for calculating a weighted average value of color difference data that is output of the median filter and the color difference data of the target pixel, and for outputting color difference data as the new color difference data.