1. An image processing device comprising: circuitry configured to: calculate a ratio between a first size of an interest region that is a region of an interest subject, and a second size of a partial region that is a region of a portion of said interest subject included in said interest region, of an image, said interest region being a part of said image less than an entire region of said image; compare the first size of said interest region, and a predetermined target size of said image; and control a zoom of said image so that said ratio calculated by said circuitry, and a predetermined value match or generally match, and that a difference between the first size of said interest region, and said predetermined target size is smaller than a predetermined threshold.