NetGraphicsintroduction to computer graphics

Bresenham algorithm for a line

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Bresenham algorithm for a line interactivity: select starting point of a line and moving with mouse transfer ending points.

Bresenham algorithm for a line[4]

// draw a line from point x1,y1 into x2,y2
public void bresenham_line(int x1, int y1, int x2, int y2) { 
	// if point x1, y1 is on the right side of point x2, y2, change them
	if ((x1 - x2) > 0) {bresenham_line(x2, y2, x1, y1); return;}
	// test inclination of line
	// function Math.abs(y) defines absolute value y
	if (Math.abs(y2 - y1) > Math.abs(x2 - x1)) {
		// line and y axis angle is less then 45 degrees
		// that swhy go on the next procedure
		bresteepline(y1, x1, y2, x2); return; 
	}
	// line and x axis angle is less then 45 degrees, so x is guiding
	// auxiliary variables
	int x = x1, y = y1, sum = x2 - x1, Dx = 2 * (x2 - x1), Dy = Math.abs(2 * (y2 - y1));
	int prirastokDy = ((y2 - y1) > 0) ? 1 : -1;
	// draw line
	for (int i = 0; i <= x2 -x1; i++) {
		setpix(x, y);
		x++;
		sum -= Dy;
		if (sum < 0) {y = y + prirastokDy; sum += Dx;}
	}
}

public void bresteepline(int x3, int y3, int x4, int y4) {
	// if point x3, y3 is on the right side of point x4, y4, change them
	if ((x3 - x4) > 0) {bresteepline(x4, y4, x3, y3); return;}

int x = x3, y = y3, sum = x4 - x3,	Dx = 2 * (x4 - x3), Dy = Math.abs(2 * (y4 - y3));
	int prirastokDy = ((y4 - y3) > 0) ? 1 : -1;

for (int i = 0; i <= x4 -x3; i++) {
		setpix(y, x);
		x++;
			sum -= Dy;
		if (sum < 0) {y = y + prirastokDy; sum += Dx;}
	}
}