Recursive representation and progressive display of binary objects for efficient network browsing

Abstract

When binary objects are browsed in a network environment, data transmission rate, progressive display capability, and view modification under rotation, scaling, and/or translation (R/S/T) are the major factors for selection of an appropriate representation model of binary objects. A new half-plane-based representation and display method for 2D binary objects is proposed. Within this modeling framework, a binary object approximated by a shape of a polygon can be represented as a collection of half-planes defined over the edges of the polygon under operations of union and intersection. The basic shape attributes of the object model are the slope and the y-intercept of the boundary line of the constituent half planes. In the progressive display of the binary object our method adopts the quadtree block subdivision to divide the object image into hierarchical levels of detail (or resolution). Our method determines the color of a quadtree node based on the (angle, intercept) representation parameters. It is shown that the representation parameters at the parent node are recursively related to those at the child nodes, This recursive relation is crucial for deriving the color of the nodes for progressive object display. Lemmas for the node color determination for an object expressed in the form of half-planes, a convex polygon, or a concave polygon are derived step by step. Our method is generally better than many existing methods in terms of data transmission rate, progressive display capability, and view modification under R/S/T variations. Simulation results are provided to illustrate the performance of our method. (C) 1998 Academic Press.