Method Bounds

path.go:1108–1230

Bounds returns the exact bounding box rectangle of the path.

()

// Bounds returns the exact bounding box rectangle of the path.
func (p *Path) Bounds() Rect {
	if len(p.d) < 4 {
		return Rect{}
	}

	// first command is MoveTo
	start, end := Point{p.d[1], p.d[2]}, Point{}
	xmin, xmax := start.X, start.X
	ymin, ymax := start.Y, start.Y
	for i := 4; i < len(p.d); {
		cmd := p.d[i]
		switch cmd {
		case MoveToCmd, LineToCmd, CloseCmd:
			end = Point{p.d[i+1], p.d[i+2]}
			xmin = math.Min(xmin, end.X)
			xmax = math.Max(xmax, end.X)
			ymin = math.Min(ymin, end.Y)
			ymax = math.Max(ymax, end.Y)
		case QuadToCmd:
			cp := Point{p.d[i+1], p.d[i+2]}
			end = Point{p.d[i+3], p.d[i+4]}

			xmin = math.Min(xmin, end.X)
			xmax = math.Max(xmax, end.X)
			if tdenom := (start.X - 2*cp.X + end.X); !Equal(tdenom, 0.0) {
				if t := (start.X - cp.X) / tdenom; IntervalExclusive(t, 0.0, 1.0) {
					x := quadraticBezierPos(start, cp, end, t)
					xmin = math.Min(xmin, x.X)
					xmax = math.Max(xmax, x.X)
				}
			}

			ymin = math.Min(ymin, end.Y)
			ymax = math.Max(ymax, end.Y)
			if tdenom := (start.Y - 2*cp.Y + end.Y); !Equal(tdenom, 0.0) {
				if t := (start.Y - cp.Y) / tdenom; IntervalExclusive(t, 0.0, 1.0) {
					y := quadraticBezierPos(start, cp, end, t)
					ymin = math.Min(ymin, y.Y)
					ymax = math.Max(ymax, y.Y)
				}
			}
		case CubeToCmd:
			cp1 := Point{p.d[i+1], p.d[i+2]}
			cp2 := Point{p.d[i+3], p.d[i+4]}
			end = Point{p.d[i+5], p.d[i+6]}

			a := -start.X + 3*cp1.X - 3*cp2.X + end.X
			b := 2*start.X - 4*cp1.X + 2*cp2.X
			c := -start.X + cp1.X
			t1, t2 := solveQuadraticFormula(a, b, c)

			xmin = math.Min(xmin, end.X)
			xmax = math.Max(xmax, end.X)
			if !math.IsNaN(t1) && IntervalExclusive(t1, 0.0, 1.0) {
				x1 := cubicBezierPos(start, cp1, cp2, end, t1)
				xmin = math.Min(xmin, x1.X)
				xmax = math.Max(xmax, x1.X)
			}