<Boundary fill>=
stack.push (seed);
while (stack.notEmpty()) {
pixel = stack.pop();
pixel.plot(color);
nghbrs = pixel.neighbors();
while (nghbrs) {
neighbor = nghbrs.getPixel();
if (neighbor.interior() && neighbor.notColored(color)) {
stack.push(neighbor);
nghbrs = nghbrs.next();
}
}
}