An image processor includes: a reduction (resizing) processor 102 that reduces an original image obtained from a single-sensor color imaging device to an image conforming to a display size of a display monitor; and a rearranged color array display data generation processor 103 that generates one or more types of color array images conforming to a color pixel array of the display monitor, based on the reduced image. With this configuration, one or more types of display reduced-size image having color information of the original image are generated. Thus, a small-size image for display generated from a large-size original image output from an imaging device can be displayed at high speed with a minimum frame delay.