Function drawLine

plot.go:292–329

Algorithm for drawing line between two points http://en.wikipedia.org/wiki/Bresenham's_line_algorithm

(x0, y0, x1, y1 int, plot func(int, int))

//
// http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
func drawLine(x0, y0, x1, y1 int, plot func(int, int)) {
	dx := x1 - x0
	if dx < 0 {
		dx = -dx
	}
	dy := y1 - y0
	if dy < 0 {
		dy = -dy
	}
	var sx, sy int
	if x0 < x1 {
		sx = 1
	} else {
		sx = -1
	}
	if y0 < y1 {
		sy = 1
	} else {
		sy = -1
	}
	err := dx - dy

	for {
		plot(x0, y0)
		if x0 == x1 && y0 == y1 {
			break
		}
		e2 := 2 * err
		if e2 > -dy {
			err -= dy
			x0 += sx
		}
		if e2 < dx {
			err += dx
			y0 += sy
		}
	}
}