The present invention provides an image forming apparatus that forms an image corresponding to light emitted from a light source. The apparatus comprises: an image processing unit that generates image data having a first resolution and generates tag information that indicates whether to perform image processing and is associated with each of the pixels of the image data having the first resolution; a converter that converts the image data having the first resolution to image data having a second resolution higher than the first resolution; a light source driver that drives the light source using a modulation signal that corresponds to the image data having the second resolution; an identifying unit that identifies a target pixel to be subjected to image processing in the image data having the first resolution on a basis of the tag information; and a pattern generator that generates an image-processed pixel pattern having the second resolution according to the target pixel, wherein the converter converts the target pixel in the image data having the first resolution to the generated image-processed pixel pattern.