An image forming apparatus includes a photoconductor, a light source, and circuitry that receives: first image data including first pixels each indicating image density or one of turning on and off the light source; and tag data indicating an attribute of each first pixels. The circuitry sets specific data to identify a first target pixel subjected to change out of the first pixels, converts the first image data into second image data having a higher resolution than that of the first image data, and controls the light source according to the second image data to form an image. In conversion, the circuitry identifies a second target pixel corresponding to the first target pixel out of second pixels of the second image data according to the specific data and the tag data, and changes the second target pixel into a pixel to turn on the light source.