Method and apparatus for determining boundaries of graphic regions

Abstract

The present invention provides apparatus and methods for determining the boundaries of arbitrarily shaped regions on a computer display system having a central processing unit (CPU). The CPU is coupled to a display having a plurality of selectively enabled and disabled display elements arranged in a matrix, whereby each display element is identified by a unique X,Y address. A memory coupled to the CPU includes a plurality of memory cells, wherein the cells correspond to a display element on the display. An initial X,Y address is selected on the display by a user employing a cursor control to identify an area on the display where the boundaries of a region are to be determined. The initial X,Y address selected by the user is defined as a seed cell. The CPU determines if the initial seed cell corresponds to a disabled memory cell and blank (disabled) display element, and in such event increments the initial X,Y address to search outwardly a predetermined maximum distance to adjacent memory cells until an enabled (non-blank) cell is located. This enabled cell is set as a new seed cell. The CPU then searches radially outward in M directions from the new seed cells X,Y address for N consecutive disabled (blank) memory cells and sets in each of these directions the last non-blank (enabled) memory cell prior to the N consecutive disabled cells, as boundary cells. An initial rectangular region is defined through at least two of these boundary cells, and the CPU determines if P consecutive rows and columns of blank (disabled) memory cells bound the initial rectangular region. If not, the CPU selectively extends the boundaries of the initial rectangular region in X and Y directions until the region is bounded by P consecutive rows and columns of disabled cells. Accordingly, the boundaries of a region on a display are determined.