Provided is a data processing apparatus for calculating confidence coefficient data to indicate a confidence of pixel values of a second image data. The apparatus acquires similarity between a pixel value of a first pixel of the first image data corresponding to a target pixel of the confidence coefficient data, and each pixel value of a plurality of second pixels around the first pixel. The apparatus acquires the confidence coefficient by determining an estimated pixel value in the third pixel of the second image data corresponding to the first pixel, based on the similarity of each of the plurality of second pixels, each pixel value of the plurality of fourth pixels around the third pixel and the pixel value of the third pixel and by comparing the pixel value of the third image and the estimated pixel value in the third pixel.