1. An image forming apparatus comprising: a scanning unit configured to deflect a light beam in a scanning direction to form an image on a photosensitive member; a receiving unit configured to receive image data and control data via a bus having a predetermined bit width, wherein the receiving unit receives the control data using a part that is not used for the image data in the predetermined bit width; a distortion correction unit configured to correct the image data received by the receiving unit based on a distortion of a scan line of the light beam deflected by the scanning unit; a smoothing unit configured to perform a smoothing on the image data corrected by the distortion unit; and a control unit configured to control, based on control data corresponding to a pixel of interest, the smoothing on image data of the pixel of interest.