An image forming apparatus includes a positioning unit that acquires a misalignment amount of a pixel in a main-scanning direction and a sub-scanning direction, the pixel as a reference pixel for zooming image data, and decides a position of a pixel as a correction target, based on the misalignment amount; a correcting unit that corrects the pixel; a zooming unit that controls the positioning unit and the correcting unit so as to repeatedly perform the positioning process and the correction process on a pixel line; a pattern recognition unit that performs pattern matching on a predetermined pattern and a predetermined pixel line; and a pixel position changing unit that shifts the decided pixel position in the sub-scanning direction, wherein the zooming unit performs the zooming process on the pixel line of the sub-scanning direction including the pixel that is located at shifted pixel position.