1. An image processing apparatus, comprising: a dividing unit that divides an area including viewpoints of images into a plurality of sub-areas; a selecting unit that selects one image as a first image from a plurality of images in each sub-area, respectively, and configured to define other images of the plurality of images as second images in each sub-area, respectively; a depth generating unit that generates a depth map of the first image and a depth map of the second image, the depth maps indicating a depth value of a pixel of a corresponding image; a projective transformation unit that generates a projected depth map of the second image of the second images from the depth map of the first image; a subtracting unit that creates a difference map of the second image, the difference map being a difference between the depth map of the second image and the projected depth map of the second image; and a storage unit that stores the depth map of the first image and the difference map of the second image, wherein each of the depth generating unit, projective transformation unit, subtracting unit, and storage unit operates independently on the first and second images of each of the sub-areas in the plurality of sub-areas.