Patent ID: 7899244

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 or not a target pixel is a pixel constituting any of a monotone increasing part and a 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, each positioned on an opposite side of the target pixel in the sub-scanning direction, with a luminance change detection circuit; by calculating new color difference data with a color difference data calculation circuit, wherein in the case the target pixel is determined to be a pixel constituting any of a monotone increasing part and a monotone decreasing part of a luminance value of the input image, by employing a median filter to the color difference data of the target pixel and the neighboring pixel and for outputting from the median filter color difference data as the new color difference data, and wherein in the case the target pixel is determined not to be a pixel constituting any of a monotone increasing part and a monotone decreasing part of a luminance value of the input image, by employing the 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 the weighted average value of color difference data as the new color difference data; and synthesizing the new color difference data obtained from 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.