Anti-aliasing raster operations

Abstract From the Canadian patent

A method and apparatus for performing anti-aliasing of rendered lines, text and images displayed by a workstation on a video display. The anti-aliasing is performed by logically dividing each addressable frame buffer pixel into sixteen sub-pixels and generating a gray scale value for the displayed pixel that is a function of the number of subpixels crossed by a portion of a rendered image. The invented circuitry is part of the circuitry used for combining source and destination data which forms the displayed image namely, an anti-aliasing mask and filter adder/subtractor logic, saturation logic and anti-aliasing logic.