COMPUTER SYSTEM PROCESS AND USER INTERFACE FOR PROVIDING INTELLIGENT SCISSORS FOR IMAGE COMPOSITION

A video editing system capable of tracing and extracting objects in an image selects edges of the object to be traced based on an edge cost computation and on a rotational amount of the edge. The edge cost calculation method modulates the gradient magnitude of the pixel against the gradient direction of an edge to reduce the ambiguity often encountered during tracing as a result of background noise in the image. A method of editing the trace involves introducing control points between previously generated points in the trace. Because of a consistent edge selection criteria, based on a rotational amount of an edge, the characteristics of the previous edge are preserved, and an iterative editing process is eliminated. By basing the selection criteria on a rotation of the path, a total path rotation may be maintained with minimal extra compute operations.