draw2d/draw2dbase/line.go
2015-08-27 14:12:22 +02:00

58 lines
977 B
Go

// Copyright 2011 The draw2d Authors. All rights reserved.
// created: 27/05/2011 by Laurent Le Goff
package draw2dbase
import (
"image/color"
"image/draw"
)
func abs(i int) int {
if i < 0 {
return -i
}
return i
}
// PolylineBresenham draws a polyline to an image
func PolylineBresenham(img draw.Image, c color.Color, s ...float64) {
for i := 2; i < len(s); i += 2 {
Bresenham(img, c, int(s[i-2]+0.5), int(s[i-1]+0.5), int(s[i]+0.5), int(s[i+1]+0.5))
}
}
// Bresenham draws a line between (x0, y0) and (x1, y1)
func Bresenham(img draw.Image, color color.Color, x0, y0, x1, y1 int) {
dx := abs(x1 - x0)
dy := abs(y1 - y0)
var sx, sy int
if x0 < x1 {
sx = 1
} else {
sx = -1
}
if y0 < y1 {
sy = 1
} else {
sy = -1
}
err := dx - dy
var e2 int
for {
img.Set(x0, y0, color)
if x0 == x1 && y0 == y1 {
return
}
e2 = 2 * err
if e2 > -dy {
err = err - dy
x0 = x0 + sx
}
if e2 < dx {
err = err + dx
y0 = y0 + sy
}
}
}