Method and system for double error antialiasing in a computer display system

A data processing system for generating and displaying an antialiased approximation of a line, said data processing system comprising:

• a graphics adapter including:
• an input for receiving a graphics data stream;
• means, responsive to receiving, in said memory, a line in said graphics data stream, for generating a plurality of parameters according to Bresenham's algorithm for said line, wherein said plurality of parameters comprises a first error term and a second error term;
• means for generating a pixel intensity for an initial pixel for a pixel approximation of said line;
• means for comparing said first error term with a threshold to determine an amount of error;
• means for adjusting said first error term by a first selected amount in response to said means for comparing said first error term and means for adjusting said second error term by a second selected amount in response to said means for comparing of said first error term;
• means for selecting a first pixel proximate to said initial pixel comprising means for comparing said first adjusted error term with a second threshold to locate a pixel closest to an intersection of said line and a minor axis and means for assigning said first pixel a first intensity based on said comparison of said second adjusted error term with said first error term;
• means for selecting second pixel proximate to said first pixel in response to means for selecting said first pixel and means for assigning said second pixel a second intensity based on said comparison of said second adjusted error term with said first error term;
• and
• a raster-scan device, coupled to said graphics adapter, for generating images within a two-dimensional grid comprising rows and columns of pixels, wherein an antialiased approximation of a line may be displayed utilizing assigned pixel intensities from the graphics adapter.