Abstract: A scan conversion device generates segment direction information on the basis of vector information representing outlines of a pattern such as graphic FIGURES. An image drawing data generating device generates raster information inclusive of image drawing direction information in accordance with predetermined image drawing direction rules on the basis of the segment direction information, and further generates new image drawing data to be stored into a frame memory in accordance with predetermined image drawing rules on the basis of the raster information and previous image drawing data read from the corresponding memory area of the frame memory. The frame memory stores the image drawing data on a dot-by-dot basis. A dot pattern converting device converts the image drawing data provided from the frame memory into a dot pattern signal in accordance with an image drawing mode as set.