1. An image processor comprising: an image input unit that obtains an image captured by an imaging device installed on a vehicle; a vehicle information input unit that obtains a distance between the vehicle and a road junction or curve in a traveling direction of the vehicle based on information received from a vehicle-mounted device installed in the vehicle; a recording unit in which imaging information indicating properties of the imaging device and driver information regarding a visual field of a driver of the vehicle are stored; a magnifying object recognition unit that recognizes a certain magnifying object in the captured image; and a composing unit that produces, when the magnifying object recognition unit recognizes the certain magnifying object, a composite image of a magnified image of the magnifying object and the captured image, wherein the composing unit uses the distance obtained by the vehicle information input unit as well as the imaging information and the driver information stored in the recording unit to determine a non-blind spot area in the captured image that does not include an image of a blind spot for the driver, and produces the composite image such that the magnified image is superimposed on the non-blind spot area.