Binary data (VDO) developed to a dot pattern are sequentially stored in line memories (1-9). A processing circuit (43) is constituted by a logic calculation circuit, and determines an edge portion of an image or a halftone image on the basis of 11.times.9 pixel data in shift registers (34-43). When the edge portion of an image is determined, data of a pixel of interest is converted to data that can print a smooth edge portion. Changed data (VDOM) is converted again according to the type of toner. The converted signal is supplied to a laser driver of a printer, and a printing operation is performed by scanning a laser. A resolution setting unit (1700) receives a resolution setting command from an external apparatus (1300), and sets a designated resolution in a printer (1200) according to the resolution setting command. The resolution setting unit (1700) divides one pixel into an optimal number of pixel sections on the basis of the designated resolution, and sets a logic circuit for performing optimal smoothing processing for divided data in a smoothing unit (1018). Bit map development based on code data supplied from the external apparatus (1300), and smoothing processing according to a smoothing logic, are performed.