Filtering edges for gray-scale displays

Abstract

While simple line-drawing techniques produce “jagged” lines on raster images, more complex anti-aliasing, or filtering, techniques use gray-scale to give the appearance of smooth lines and edges. Unfortunately, these techniques are not frequently used because filtering is thought to require considerable computation. This paper presents a simple algorithm that can be used to draw filtered lines; the inner loop is a variant of the Bresenham point-plotting algorithm. The algorithm uses table lookup to reduce the computation required for filtering. Simple variations of the algorithm can be used to draw lines with different thicknesses and to smooth edges of polygons.