A connection unit receives image data to be printed and image information on a type of the image data from an external device. A pseudo-halftone processing unit converts the image data into pseudo-halftone image data. When the image information received from the external device indicates that the type of the image data is a point-of-purchase advertising image, the pseudo-halftone processing unit performs a pseudo-halftone processing on the image data at a quantization level of three or more bits on a pixel and takes a growth order causing all pixels in a low-density area to grow averagely.