GRAPHIC OUTPUT DEVICE

PURPOSE:To enhance an effect of anti-aliasing process by correcting a state that lateral lines are expressed thinner than vertical lines at the time of outputting from a laser beam printer, etc., by using a filter of long vertical length when dividing a pixel to be used into subpixels, filtering it, and adding them in one pixel to calculate an area rate. CONSTITUTION:If a width ratio of a vertical line to a lateral line is c:1 and a subpixel division of m*m is used, when the vertical length of a filter is x=m(c-1)/2, it is extended by a value obtained by multiplying 2/m by the round-up fraction of the x. The total of one pixel part at the center of the filter is obtained, and the standard value of the filter is set to A. Since the filter has a vertical length of one pixel or more, an image to be filtered by the filter needs (1 + (round-up fraction of x) X 2/m) line, and hence image data of the line is always stored while updating the content. The image data of a plurality of the lines is divided into subpixels, and filtered by a filter having long vertical length to obtain an area rate. If the calculated value is larger than the value A of the filter, the value is replaced by a.