Anti-aliasing raster scan display system

Abstract

A raster scan display system for eliminating jagged edges from vectors or polygon boundaries inclined within .+-.45 degrees to horizontal comprising a digital vector generator, a frame buffer memory, a color look-up table, digital-to-analog converters and convolvers placed in front of each digital-to-analog converter for each video output stage of the color look-up table. Fractional address data are appended to each pixel written into the frame-buffer memory to specify the true location of the pixel more accurately. Intensity data for each of the colors assigned thereto by the color look-up table are convolved with a kernel that is selected by the Y fractional address. The convolvers also process the X fractional address which controls the boundaries between pixels on a scan line. Fractional address data read out of the frame-buffer controls the kernels in the convolvers to render the positioning of pixels at four times the addressability of the frame-buffer. Each pixel is micropositioned to an accuracy that is approximately one quarter of the CRT spot diameter. The convolvers double the number of displayed lines, allow for a very rapid rendition of the displayed image, and operate at the troughput of the graphics display system. Memory size is also reduced and image quality greatly enhanced.