According to some embodiments, an image processor includes a perspective image generator, a perspective image acquirer, a corresponding point acquirer, a first calculator and a display image generator. The first calculator updates the position of the one or more first corresponding point on the first perspective image, based on a difference in position between the first and second perspective images. The display image generator generates a first display image including the first and second perspective images, the one or more first corresponding points updated on the first perspective image, and the one or more second corresponding points on the second perspective image. The perspective image generator changes the first direction into a third direction based on the difference in position between the first and second perspective images, and generates an updated one, viewed in the third direction, of the first perspective image.