A projection conversion coefficient acquirer of an image processing apparatus acquires the same number of projection conversion coefficients, which are coefficients for doing projection conversion of an image, as the number of a plurality of reference points at differing positions in the image. A post-projection-conversion image acquirer does projection conversion on the image through each of the projection conversion coefficients, of which there are the same number as the number of the plurality of reference points acquired by the projection conversion coefficient acquirer, and acquires a plurality of post-projection-conversion images from the image, the number of the post-projection-conversion images being the same as the number of reference points. A weighted averager finds a weighted average for each of the coordinates of pixels comprising the plurality of post-projection-conversion images, using a plurality of weightings determined in accordance with distance from the plurality of reference points in the image. A weighted average image acquirer acquires a weighted average image in which the plurality of post-projection-conversion images have undergone weighted averaging by the weighted averager.