Method and apparatus for antialiasing raster scanned images

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT In the discussion of the background art above, a two-pixel wide line drawing process was described as an improved implementation of the basic Bresenham process.
In accordance with Sfarti, it was indicated that it was not necessary to accurately accommodating for the effect of a third intersected pixel on the line to be drawn.
It has been found, however, that projected lines can be rendered more correctly in accordance with the three pixel wide line drawing process of the present invention.
By drawing a three pixel wide line, the effect of a third intersected pixel can be accurately factored into the rendered line.
A process, in accordance with the preferred embodiment of the present invention, for drawing a three pixel wide line is described as follows: Select a first pixel closest to an idealized line between the start point and the end point of the line; select a second pixel adjacent to the first pixel, such that the first pixel and the second pixel form a pair of pixels straddling the idealized line; select a third pixel adjacent to the first pixel, such that the second pixel and the third pixel frame the first pixel so as to form a line of pixels; determine a first coverage for the first pixel as a function of a value of a distance between the idealized line and the first pixel (First.
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-- Coverage =s=(1+d/dx)/2) determine a second coverage for the second pixel as a function of a value of a distance between the idealized line and the second pixel (Second.
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-- Coverage =t=(1-d/dx)/2); determine a third coverage for the third pixel as a function of a value of a distance between the idealized line and the third pixel (Third.
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-- Coverage =min(t+1, s+1); determine an intensity for the line of pixels as a function of the first coverage, the second coverage, and the third coverage; write color values into a frame buffer memory for the line of pixels based on the intensity of the line of pixels; output the color values for the line of pixels to a display; and repeat the above steps until color values for each of a plurality of adjacent lines of pixels between the start point and the end point have been output to the display