Boundary-Fill Algorithm

Boundary-Fill Algorithm

Another approach to area filling is to start at a point inside a region and paint the

interior outward toward the boundary. If the boundary is specified in a single

color, the fill algorithm proceeds outward pixel by pixel until the boundary color

is encountered. This method, called the boundary-till algorithm

A boundary-fill procedure accepts as input the coordinates of an interior

point (x, y), a fill color, and a boundary color. Starting from (x, y), the procedure

tests neighboring positions to determine whether they are of the boundary color.

If not, they are painted with the fill color, and their neighbors are tested. This

process continues until all pixels up to the boundary color for the area have been

tested. Both inner and outer boundaries can be set up to specify an area, and

some examples of defining regions for boundary fill

two methods for proceeding to neighboring pixels from

the current test position.

void boundaryFill4 (int x, int y, int fill, int boundary)

(

int current:

current = getpixel (x, y);

if ((current != boundary) && (current != fill)) {

setcolor (fill);

setpixel (x, y):

boundary~ill4 (x+l, y, fill, boundary);

boundaryFill4 (x-1, y, fill, boundary) :

boundaryFill4 (x, y+l, fill, boundary);

boundaryFill4 (x, y-1, fill, boundary) ;

)