Image processing device, image reading apparatus, image processing method

An image processing method of correcting, in two-dimensional target image data, pixel data that includes noise, the image processing method comprising:

• sequentially selecting, from the target image data, data of a 3×3 target pixel group that is made up of one pixel of interest and eight neighboring pixels that neighbor the pixel of interest;
• selecting, for each piece of data of the target pixel group, sample pixels from the eight neighboring pixels, according to a predetermined rule;
• calculating, for each piece of data of the target pixel group, a sample average value that is an average value of data of the sample pixels;
• and
• replacing, for each piece of data of the target pixel group, data of the pixel of interest with a correction value that is based on the sample average value, on a necessary condition that a difference of interest, that is a difference between the data of the pixel of interest and the sample average value, exceeds a predetermined correction reference range, wherein
• in the selecting of the sample pixels, the image processing method includes selecting, as a target line, each of four reference lines that respectively pass through the pixel of interest in a row direction, a column direction, and two diagonal directions that intersect the row and column directions, and
• selecting, on a necessary condition that a difference between data of a pair of the neighboring pixels that are positioned neighboring the pixel of interest along the target line, is within a predetermined first selection reference range, and that with respect to at least one of two areas on both sides of the target line, all differences among data of three neighboring pixels that exist in the area are within a predetermined second selection reference range, the pair of neighboring pixels as the sample pixels.