1. An image processor comprising: an acquisitor that acquires information regarding shape of a projection surface on which a first image is projected, information regarding position of a viewpoint for observing the first image projected on the projection surface, and information regarding position of a projection point for projecting the first image; a predictor that predicts a viewable region in which the first image projected on the projection surface is viewable from the viewpoint based on the acquired information regarding the shape, the acquired information regarding the viewpoint, and the acquired information regarding the projection point; and a corrector that corrects a second image to generate the first image, the second image being set within the viewable region.