Xiaolin Wu's line algorithm: Difference between revisions

Revision as of 19:59, 17 June 2005

Revision as of 18:21, 23 June 2005

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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 (It is still slower than [[Bresenham's line algorithm|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>). The extension to cover nearly-vertical lines is trivial, and left as an exercise for the reader.

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</code>

An extension to the algorithm for circle drawing was presented by Xiaolin Wu in the book ''Graphics Gems II''. Just like the line drawing algorithm is an replacement for of [[Bresenham's line algorithm]], the circle drawing algorithm is a replacement for Bresenham's circle drawing algorithm.

==References==