Method for Defining, Drawing and Filling an Ellipse to the Limit of Resolution of the Display Device Using an Integer Interface
Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2005-Feb-15
A high-performance, device-independent, integer-based method to draw and fill both orthogonal and off-axis ellipses is described. A new series of commands are defined within the Graphics Support Library (GSL) on the IBM RT/PC: gsell(), gsfell(), gsearc(). These commands draw and fill ellipses and draw elliptical arcs. The interface requires a center point of the ellipse, the semi-major and semi- minor axis, and the angle between the major axis and x axis (for orthogonal ellipses this angle is zero). The angle is specified in tenths of degrees, with full rotation being 360o . All parameters are integers. The algorithm calculates the ellipse, using integer functions, as a set of polylines. Each of these polylines has an optimal length as to the size of the device it will be rendered on.