Geometrical, topological, and hierarchical structuring of overlapping 2-D discrete objects

A model of scenes composed of 2-D discrete objects is presented. A generalization of the 2 1/2 - D positioning features usually implemented in 2 1/2 - D environment is given, treating object superimposition. The positioning representation sits on an explicit topological and geometrical encoding of object boundaries. This approach allows structured manipulations of objects (intersection, combination,...) and efficient redisplay of scene, such that every modified pixel is drawn exactly once. Moreover, this model is consistent from a geometrical and topological point of view and allows the construction of a scene from a digital image. Many applications can be considered: graphics editors, paintboxes, image processing environments, etc. (C) 1997 Elsevier Science Ltd. All rights reserved.