for (int y = upper_left.y; y <= lower_right.y; y += px_size) {
for (int x = upper_left.x; x <= lower_right.x; x += px_size) {
Point point = new Point(x, y);
for (int y = upper_left.y; y <= lower_right.y; y += px_size) {
for (int x = upper_left.x; x <= lower_right.x; x += px_size) {
Point point = new Point(x, y);