GRAPHICS PROCESSING APPARATUS FOR PRODUCING OUTPUT OATH AT EDGES OF AN OUTPUT IMAGE DEFINED BY VECTOR DATA

A graphics processing apparatus carries out an antialiasing for obtaining an output image having smooth edges, enabling a speedy computation of approximate shading area rates of pixels by making use of neither a subpixel dividing process nor a shading pixel counting process. The apparatus comprises a discriminating part for discriminating the presence of an end point pixel at an edge portion of an image defined by a vector data, a computing part for computing the number of edge pixels by extracting two integer parts a, b from x coordinate values Xa, Xb of two points where a scanline intersects the vector data, a setting part for setting a x coordinate value of the end point pixel to the Xb only when an end point pixel is found at the edge portion, an approximate point part for determining an approximate point value C' from a prescribed factor c.times.(n-1) computed by a decimal fraction c extracted from the x coordinate value Xa, a memory part for storing a lookup table containing a set of predetermined data, and an approximate area factor part for determining an approximate shading area factor k by making reference to the lookup table stored in the memory part.