An image processing apparatus includes a correcting unit that performs enlarging or reducing correction on an image to be processed by determining an arrangement of pixels that are to be added to or deleted from gradational image data of the image to be processed based on an angle at which the pixels are to be arranged with respect to a horizontal direction of the image to be processed or with respect to a vertical direction of the image to be processed, and a pixel array control unit that changes the angle at which the pixels are arranged based on a test image of the image data to be processed after being corrected by the correcting unit.