Pixel accurate edges for scanline rendering system

Abstract

A method () of converting a monotonic curve into edge information is disclosed. A method (A) of determining an integer edge crossing value, Xi, for a new edge crossed by a scanline (i.e., an inactive edge being crossed by the scanline for the first time) is also disclosed. Further, a method (B) of determining an integer edge crossing value, Xi, for an active edge crossed by a scanline, is also disclosed. The disclosed methods have general application in the representation of monotonic curves. The described methods allow monotonic curves to be accurately represented in terms of edges where the original curve can be reconstructed from the edges. Furthermore, the methods allow edge tracking to be performed such that any resulting error is restricted to a fixed-point division error. At transition points between adjoining segments, an original edge crossing point may be determined to avoid accumulated error.