An image forming apparatus includes an image processor, a converter, a light source driver, an identifying unit, and a pattern generator. The image processor generates image data of first resolution and generates tag information indicating whether to perform image processing and associated with pixels of the image data of first resolution. The converter converts the image data of first resolution to image data of a higher second resolution. The light source driver drives a light source using a modulation signal corresponding to the image data of second resolution. The identifying unit identifies a target pixel to be subjected to image processing in the image data of first resolution based on the tag information. The pattern generator generates an image-processed pixel pattern of the second resolution according to the target pixel. The converter converts the target pixel in the image data of first resolution to the generated image-processed pixel pattern.