1. An image processing device comprising: a target data extracting unit configured to extract, as target data, a set of signal values of pixels included in a target region including a target pixel in an input image; a reference data obtaining unit configured to obtain, as reference data for each of a plurality of reference pixels corresponding to the target pixel, a set of signal values of pixels included in a reference region including the reference pixel; a transformation reference data generating unit configured to generate transformation reference data from the reference data and output a plurality of signal values of transformation reference pixels which the generated transformation reference data has; a weight determining unit configured to determine a weight for each of the plurality of transformation reference pixels based on the target data and the reference data; and a unit configured to generate an output pixel corresponding to the target pixel by using a signal value calculated based on the transformation reference pixels and the weights, wherein the transformation reference data generating unit generates the transformation reference data by transforming the reference data in which a number of the pixels included in the reference region is larger than a number of the pixels included in the target region based on the number of the pixels included in the target region and the number of the pixels included in the reference region.