Xiaolin Wu's line algorithm: Difference between revisions

Revision as of 00:38, 9 August 2006

Revision as of 21:38, 17 August 2006

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'''Xiaolin Wu's line algorithm''' is an [[algorithm]] for line [[antialiasing]], which was presented in the article ''An Efficient Antialiasing Technique'' in the July [[1991]] issue of ''[[Computer Graphics]]'', as well as in the article ''Fast Antialiasing'' in the June [[1992]] issue of ''[[Dr. Dobb's Journal]]''.

[[Bresenham's line algorithm|Bresenham's algorithm]] draws lines extremely quickly, but it cannot perform anti-aliasing. In addition, it cannot handle the case where the line endpoints do not lie exactly on integer points of the pixel grid. A naïve approach to anti-aliasing the line would take an extremely long time, but Wu's algorithm is quite fast (Itit is still slower than Bresenham's, though). The basis of the algorithm is to draw pairs of pixels straddling the line, coloured according to proximity. Pixels at the line ends are handled separately. Lines less than one pixel long should be handled as a special case.

Here is [[pseudocode]] for the nearly-horizontal case (<math>\Delta x > \Delta y</math>). To extend the algorithm to work for all lines, swap the x and y coordinates when near-vertical lines appear (for reference, see [[Bresenham's line algorithm]]).