1. An image processing device for processing target image data, comprising: a color component acquisition unit that, from target image data, acquires a luminance component, a first color difference component, and a second color difference component which represent color of respective pixels; and a smoothing processor that, at individual pixel positions of at least a partial area of a target image represented by the target image data, carries out a maximum magnitude smoothing process on the first color difference component, among the luminance component, the first color difference component, and the second color difference component.