【flutter】パスと座標変換

class _MyHomePageState extends State<MyHomePage>{

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Color.fromARGB(255, 255,255,255),
      appBar: AppBar(
        title: Text('App Name', style: TextStyle(fontSize: 30.0),),
      ),
      body:Container(
        child: CustomPaint(
          painter: MyPainter(),
        ),
      ),
    );
  }
}

class MyPainter extends CustomPainter {

  @override
  void paint(Canvas canvas, Size size){
    Path path = Path();
    Rect r = Rect.fromLTWH(50.0, 50.0, 75.0, 75.0);
    path.addOval(r);
    r = Rect.fromLTWH(75.0, 75.0, 125.0, 125.0);
    path.addOval(r);
    r = Rect.fromLTWH(125.0, 125.0, 175.0, 175.0);
    path.addOval(r);
    Paint p = Paint();
    p.color = Color.fromARGB(150, 255, 0, 0);
    p.style = PaintingStyle.fill;
    canvas.drawPath(path, p);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => true;
}

class MyPainter extends CustomPainter {

  @override
  void paint(Canvas canvas, Size size){
    Path path = Path();
    Rect r = Rect.fromLTWH(50.0, 50.0, 75.0, 75.0);
    path.addOval(r);
    r = Rect.fromLTWH(75.0, 75.0, 125.0, 125.0);
    path.addOval(r);
    r = Rect.fromLTWH(125.0, 125.0, 175.0, 175.0);
    path.addOval(r);

    canvas.save();

    Paint p = Paint();
    p.color = Color.fromARGB(150, 255, 0, 0);
    p.style = PaintingStyle.fill;
    canvas.drawPath(path, p);

    canvas.translate(0.0, 100.0);
    p.color = Color.fromARGB(150, 0, 0, 255);
    canvas.drawPath(path, p);

    p.color = Color.fromARGB(150, 0, 255, 0);
    canvas.rotate(-0.5 * pi);
    canvas.translate(-500.0, 50.0);
    canvas.scale(1 * 1.5);
    canvas.drawPath(path, p);

    canvas.restore();
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => true;
}