If a CPU is informed that ''1200x1200 dpi'' is selected from an input unit, the CPU switches a normal 8-bit RIP process with 600x600 dpi to a 1-bit RIP process with 1200x1200 dpi. Image data, which has become 1-bit data with 1200 dpi, is stored in a page memory. A pixel packing process unit executes (2x2) packing when the image data stored in the page memory is to be output from the page memory. The packed Y color image data is restored, without delay, to a normal pixel unit in a pixel division unit. The packed M color image data is restored, with a delay in a delay memory, to a normal pixel unit in the pixel division unit. The packed C color image data is restored, with a delay in the delay memory, to a normal pixel unit in the pixel division unit. The packed K color image data is restored, with a delay in the delay memory, to a normal pixel unit in the pixel division unit.