Freehand drawing containing invisible lines

Abstract

A computer based graphic editor has the capability of recognizing as a single graphic object a plurality of unconnected freehand strokes such as a signature. This makes possible editing a document with a signature, for example, without the various parts of the signature becoming separated and no longer being a viable entity. A cursor pointing device, such as a mouse with a button, is used to enter the plurality of unconnected strokes. Initially, the first point p.sub.1 at the beginning of a stroke which is the first stroke of a plurality of unconnected strokes is read and stored with the visible attribute. As long as the button is pressed, the position of the cursor is monitored and lines drawn from each successive point to the next point p.sub.2 with each point p.sub.2 being stored with the visible attribute. When the mouse button is released, the last read point position p.sub.2 is stored with the invisible attribute. When the mouse button is pressed again, the first point p.sub.1 of the next stroke is read and stored with the visible attribute, and the process repeated. When the mouse button is again pressed and released, the ending position of the previous stroke p.sub..0., the starting position of the current stroke p.sub.1 and the ending position of the current stroke p.sub.2 are compared and, if p.sub.1 and p.sub.2 are within a tolerance range and there exist no other points between p.sub.1 and p.sub.2 and if p.sub.1 and p.sub..0. are within the tolerance range, then the termination of the signature is detected.