Go version of Bresenham's line algorithm.

bresenham.go

// plotline draws a simple line on img from (x0,y0) to (x1,y1).
//
// This is basically a copy of a version of Bresenham's line algorithm
// from https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm.
func plotline(img draw.Image, c color.Color, x0, y0, x1, y1 int) {
	dx := abs(x1 - x0)
	sx := -1
	if x0 < x1 {
		sx = 1
	}
	dy := -abs(y1 - y0)
	sy := -1
	if y0 < y1 {
		sy = 1
	}
	err := dx + dy
	for {
		img.Set(x0, y0, c)
		if x0 == x1 && y0 == y1 {
			break
		}
		e2 := 2 * err
		if e2 >= dy {
			err += dy
			x0 += sx
		}
		if e2 <= dx {
			err += dx
			y0 += sy
		}
	}
}

// abs cuz no integer abs function in the Go standard library.
func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}