1. An image processing device comprising: a first acquiring unit configured to acquire a plurality of parallax images having parallax between one another; a second acquiring unit configured to acquire identification information of a parallax image to be observed from a predetermined observing point position in each of a plurality of regions into which a display area on which a three-dimensional image is configured to be displayed is divided in a first direction and in a second direction, each of the regions including at least one element image, and the element image including each pixel in the plurality of parallax images; a third acquiring unit configured to acquire luminance distribution corresponding to positional relations between the regions and the observing point position; a corrector configured to: correct pixels at positions corresponding to the regions in the parallax images into pixels of parallax images identified by the identification information, and correct luminance of pixels at positions corresponding to the regions in the parallax images into luminance of pixels of parallax images identified by the identification information according to the luminance distribution; and a first generator configured to generate the three-dimensional image from the parallax images resulting from the correction by the corrector.