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Arc Rastering Algorithm Disclosure Number: IPCOM000060750D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09

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Niblett, PD [+details]


This article describes a method of rastering an elliptic arc to an all points addressable buffer. It is applicable to a graphics display device or to a plotter or printer. The technique can be shown always to generate accurate approximations to the ideal arc, something not always possible with previous algorithms. An elliptic arc may be specified by a center point (which is taken as the origin of our coordinate system) and an analytic equation of the form f(x,y) = 0 where f(x,y) = Ax2 + 2Hxy + By2 - AB + H2 A,B >= 0 Start and stop point may also be specified if a partial arc is required. NOTE: This assumes that the center point of the arc has been coerced to lie on a real pel (picture element). This is desirable in any case as it causes the arc to appear symmetrical.