1. An image processing device, comprising: a recording unit in which a plurality of categories and information regarding camera-to-subject distances are recorded, the information regarding each of the camera-to-subject distances corresponding to each of the plurality of categories; a resize processing unit that performs one of enlargement and reduction processing for a category decision target image based upon the information regarding the camera-to-subject distances corresponding to each of the plurality of categories, so as to obtain a plurality of first images based upon the resized category decision target image; a feature amount calculation unit that calculates a plurality of first feature amounts each of which indicates a feature of the first image obtained by the resize processing unit respectively; and a decision unit that makes a category decision on the category decision target image based upon the first feature amount, the category decision being to make a decision as to which of the plurality of categories the category target image corresponds to.