Xiaolin Wu's line algorithm: Difference between revisions

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[[file:LineXiaolinWu.gif|thumb|336px|Demonstration of Xiaolin Wu's algorithm]]

'''Xiaolin Wu's line algorithm''' is an [[algorithm]] for line [[spatial anti-aliasing|antialiasing]].

==Antialiasing technique==

'''Xiaolin Wu's line algorithm''' is an [[algorithm]] for line [[Spatial anti-aliasing|antialiasing]], which was presented in the article ''"An Efficient Antialiasing Technique''" in the July 1991 issue of ''[[Computer Graphics (publication)|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 does not perform anti-aliasing. In addition, it cannot handle any cases where the line endpoints do not lie exactly on integer points of the pixel grid. A naive approach to anti-aliasing the line would take an extremely long time. Wu's algorithm is comparatively fast, but is still slower than [[Bresenham's line algorithm|Bresenham's algorithm]]. The algorithm consists of drawing pairs of pixels straddling the line, each coloured according to its distance from the line. Pixels at the line ends are handled separately. Lines less than one pixel long are handled as a special case.

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