navono/drawCurve.js

## drawCurve.js
    function drawCurve(points, tension) {
      var ctx = layer.getContext()._context;
      ctx.beginPath();
      ctx.moveTo(points[0].x, points[0].y);

      var t = (tension != null) ? tension : 1;
      for (var i = 0; i < points.length - 1; i++) {
          var p0 = (i > 0) ? points[i - 1] : points[0];
          var p1 = points[i];
          var p2 = points[i + 1];
          var p3 = (i != points.length - 2) ? points[i + 2] : p2;

          var cp1x = p1.x + (p2.x - p0.x) / 6 * t;
          var cp1y = p1.y + (p2.y - p0.y) / 6 * t;

          var cp2x = p2.x - (p3.x - p1.x) / 6 * t;
          var cp2y = p2.y - (p3.y - p1.y) / 6 * t;

          ctx.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, p2.x, p2.y);
      }
      ctx.stroke();
    }

## test.html
<!DOCTYPE html>
<html>
<head>
  <script src="https://cdn.rawgit.com/konvajs/konva/2.0.3/konva.js"></script>
  <meta charset="utf-8">
  <title>Konva Simple Line Demo</title>
  <style>
    body {
      margin: 0;
      padding: 0;
      overflow: hidden;
      background-color: #F0F0F0;
    }
  </style>
</head>
<body>
  <div id="container"></div>
  <script>
    var width = window.innerWidth;
    var height = window.innerHeight;

    var stage = new Konva.Stage({
      container: 'container',
      width: width,
      height: height
    });

    stage.on('contentContextmenu', function(evt) {
      console.log('stage');
      evt.evt.preventDefault();
    });

    var layer = new Konva.Layer();

    var redLine = new Konva.Line({
      // points: [5, 70, 140, 23, 250, 60, 300, 20, 200, 200, 300, 100, 500, 500],
      points: [50, 50, 100, 100, 150, 50, 200, 100, 250, 50, 300, 100, 350, 50],
      stroke: 'red',
      strokeWidth: 15,
      lineCap: 'round',
      lineJoin: 'round',
      // bezier: true,
    });


    layer.add(redLine);

    // add the layer to the stage
    stage.add(layer);

    function drawCurve(points, tension) {
      var ctx = layer.getContext()._context;
      ctx.beginPath();
      ctx.moveTo(points[0].x, points[0].y);

      var t = (tension != null) ? tension : 1;
      for (var i = 0; i < points.length - 1; i++) {
          var p0 = (i > 0) ? points[i - 1] : points[0];
          var p1 = points[i];
          var p2 = points[i + 1];
          var p3 = (i != points.length - 2) ? points[i + 2] : p2;

          var cp1x = p1.x + (p2.x - p0.x) / 6 * t;
          var cp1y = p1.y + (p2.y - p0.y) / 6 * t;

          var cp2x = p2.x - (p3.x - p1.x) / 6 * t;
          var cp2y = p2.y - (p3.y - p1.y) / 6 * t;

          ctx.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, p2.x, p2.y);
      }
      ctx.stroke();
    }

  drawCurve([{x:50, y:50}, {x:100, y:100}, {x:150, y:50}, {x:200, y:100}, {x:250, y:50}, {x:300, y:100}, {x:350, y:50}]);

  </script>
</body>
</html>
	function drawCurve(points, tension) {
	var ctx = layer.getContext()._context;
	ctx.beginPath();
	ctx.moveTo(points[0].x, points[0].y);

	var t = (tension != null) ? tension : 1;
	for (var i = 0; i < points.length - 1; i++) {
	var p0 = (i > 0) ? points[i - 1] : points[0];
	var p1 = points[i];
	var p2 = points[i + 1];
	var p3 = (i != points.length - 2) ? points[i + 2] : p2;

	var cp1x = p1.x + (p2.x - p0.x) / 6 * t;
	var cp1y = p1.y + (p2.y - p0.y) / 6 * t;

	var cp2x = p2.x - (p3.x - p1.x) / 6 * t;
	var cp2y = p2.y - (p3.y - p1.y) / 6 * t;

	ctx.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, p2.x, p2.y);
	}
	ctx.stroke();
	}
	<!DOCTYPE html>
	<html>
	<head>
	<script src="https://cdn.rawgit.com/konvajs/konva/2.0.3/konva.js"></script>
	<meta charset="utf-8">
	<title>Konva Simple Line Demo</title>
	<style>
	body {
	margin: 0;
	padding: 0;
	overflow: hidden;
	background-color: #F0F0F0;
	}
	</style>
	</head>
	<body>
	<div id="container"></div>
	<script>
	var width = window.innerWidth;
	var height = window.innerHeight;

	var stage = new Konva.Stage({
	container: 'container',
	width: width,
	height: height
	});

	stage.on('contentContextmenu', function(evt) {
	console.log('stage');
	evt.evt.preventDefault();
	});

	var layer = new Konva.Layer();

	var redLine = new Konva.Line({
	// points: [5, 70, 140, 23, 250, 60, 300, 20, 200, 200, 300, 100, 500, 500],
	points: [50, 50, 100, 100, 150, 50, 200, 100, 250, 50, 300, 100, 350, 50],
	stroke: 'red',
	strokeWidth: 15,
	lineCap: 'round',
	lineJoin: 'round',
	// bezier: true,
	});


	layer.add(redLine);

	// add the layer to the stage
	stage.add(layer);

	function drawCurve(points, tension) {
	var ctx = layer.getContext()._context;
	ctx.beginPath();
	ctx.moveTo(points[0].x, points[0].y);

	var t = (tension != null) ? tension : 1;
	for (var i = 0; i < points.length - 1; i++) {
	var p0 = (i > 0) ? points[i - 1] : points[0];
	var p1 = points[i];
	var p2 = points[i + 1];
	var p3 = (i != points.length - 2) ? points[i + 2] : p2;

	var cp1x = p1.x + (p2.x - p0.x) / 6 * t;
	var cp1y = p1.y + (p2.y - p0.y) / 6 * t;

	var cp2x = p2.x - (p3.x - p1.x) / 6 * t;
	var cp2y = p2.y - (p3.y - p1.y) / 6 * t;

	ctx.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, p2.x, p2.y);
	}
	ctx.stroke();
	}

	drawCurve([{x:50, y:50}, {x:100, y:100}, {x:150, y:50}, {x:200, y:100}, {x:250, y:50}, {x:300, y:100}, {x:350, y:50}]);

	</script>
	</body>
	</html>