1. A digital image processing apparatus for searching for a target image that is most similar to a reference image, in a current frame image in which each pixel has luminance data and chromaticity data, the reference image being smaller than the current frame image, the apparatus comprising: a similarity calculation unit for calculating a degree of similarity between the reference image and each of a plurality of matching images that have a same size as the reference image and are portions of the current frame image; and a target image determination unit for determining one of the plurality of matching images as the target image by using the degree of similarity that is obtained by the similarity calculation unit, wherein the similarity calculation unit calculates the degree of similarity by applying a greater weight to the chromaticity data than to the luminance data by multiplying the chromaticity data by a first coefficient that has a greater magnitude than a corresponding second coefficient that is multiplied by the luminance data.