1. A graphic display system comprising: a display unit displaying graphic images; a main memory storing graphic data in an image data region storing information on a set of unit images, including unit images having a shape defined by two contour line segments of constant luminance and sides each connecting corresponding ends of the two contour line segments, an interpolation region storing interpolation data, and a transformation region storing transformation data; and a controller for controlling processing of the graphic data, including interpolation of luminance of the unit images and transformation of coordinates of at least one vertex of each of the unit images to transform the unit images, the interpolation data being read out of the interpolation region by said controller so that the luminance of each unit image of said set of unit images is interpolated by gradually increasing the luminance from a first contour line segment of said two contour line segments toward a second contour line segment of said two contour line segments according to the interpolation data and the transformation data is read out of the transformation region by said controller so that the coordinates of the at least one vertex of each unit image of said set of unit images are shifted according to a transformation formula based on the interpolation data prior to display on said display unit of said graphic display system.