1. An image processing method comprising using a processor configured to: adapt a reference image and a plurality of images for a granulometric analysis; obtain a pattern spectrum of the reference image from the granulometric analysis; check for a similarity between the pattern spectrum and each of the plurality of images; extract a plurality of candidate images that are similar to the reference image from the plurality of images based on the granulometric analysis; transform the extracted plurality of candidate images on the basis of the reference image; calculate mutual information shared by each of the plurality of transformed candidate images and the reference image; and select a candidate image, which shares a largest amount of mutual information with the reference image, from among the plurality of transformed candidate images.