1. An image processing apparatus, comprising: a candidate pixel group determiner specify that specifies each pixel of an image to be processed as a pixel of interest, extract pixels having a divergence in position in a certain range from the pixel of interest, and determine, from the extracted pixels, pixels having a divergence in pixel value in the certain range from the pixel of interest as a candidate pixel group; an associator that associates the pixels of the candidate pixel group with the pixel of interest; and an image processor perform that performs image processing on the pixels of the candidate pixel group associated with the pixel of interest, selects pixels from the pixels of the candidate pixel group having a divergence in pixel value in the certain range from the pixel of interest as a pixel group to be processed, and smoothes a pixel value of the pixel of interest in accordance with the pixel value of each pixel of the candidate pixel group, wherein the image processor determines a number of times to repeat the image processing according to a predefined threshold, the determining of the candidate pixel group determiner is executed once for each pixel of interest, and the image processor executes the image processing for each pixel of interest the number of times.