An image forming apparatus includes: an image processor configured to perform first image processing on image data having a first resolution and to add tag data to a target pixel where second image processing is to be performed; a resolution converter configured to convert the image data into image data having a second resolution higher than the first resolution, and to perform the second image processing based on arrangement of the image data having the first resolution and the tag data; a pulse generator configured to generate an on-off modulation signal and an application-current switching signal in accordance with the image data having undergone the second image processing; and a light source driver configured to drive the light source in accordance with a current setting value output from an application current setter depending on the application-current switching signal and the on-off modulation signal.