An image forming apparatus multiplies a first clock to drive the apparatus, thereby forming a second clock, and holds (1) a frequency of a third clock used by a print unit of the apparatus, (2) a magnification setting of the multiplying, (3) a resolution of the print unit, and (4) a micro zoom ratio. The apparatus sets a magnification of the multiplying based on the held values, discriminates whether a pixel is a target pixel to which a micro zoom is executed by using the held micro zoom ratio, and switches a count comparison value of the second clock formed by the multiplying based on the discrimination, thereby forming the third clock. The apparatus then forms a pixel segment based on image data of the target pixel corresponding to the discrimination and inserts the formed pixel segment based on a period of the third clock.