HTML5 Canvas Multi-touch Scale Stage with KineticJS

Note: This lab only works on devices that support multi-touch gestures such as iOS because it makes use of multiple touch events.

Instructions: Using a mobile device that supports multi-touch gestures such as iOS, use two fingers to zoom in or out of the stage

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Code Editor

<!DOCTYPE HTML>
<html>
  <head>
    <style>
      body {
        margin: 0px;
        padding: 0px;
      }
    </style>
  </head>
  <body>
    <div id="container"></div>
    <script src="http://d3lp1msu2r81bx.cloudfront.net/kjs/js/lib/kinetic-v4.5.1.min.js"></script>
    <script defer="defer">
      var lastDist = 0;
      var startScale = 1;

function getDistance(p1, p2) {
        return Math.sqrt(Math.pow((p2.x - p1.x), 2) + Math.pow((p2.y - p1.y), 2));
      }
      var stage = new Kinetic.Stage({
        container: 'container',
        width: 578,
        height: 200,
        draggable: true,
        x: 286,
        y: 100,
        offset: [289, 100]
      });

var layer = new Kinetic.Layer();

var triangle = new Kinetic.RegularPolygon({
        x: 190,
        y: stage.getHeight() / 2,
        sides: 3,
        radius: 80,
        fill: 'green',
        stroke: 'black',
        strokeWidth: 4
      });

var circle = new Kinetic.Circle({
        x: 380,
        y: stage.getHeight() / 2,
        radius: 70,
        fill: 'red',
        stroke: 'black',
        strokeWidth: 4
      });

stage.getContent().addEventListener('touchmove', function(evt) {
        var touch1 = evt.touches[0];
        var touch2 = evt.touches[1];

if(touch1 && touch2) {
          var dist = getDistance({
            x: touch1.clientX,
            y: touch1.clientY
          }, {
            x: touch2.clientX,
            y: touch2.clientY
          });

if(!lastDist) {
            lastDist = dist;
          }

var scale = stage.getScale().x * dist / lastDist;

stage.setScale(scale);
          stage.draw();
          lastDist = dist;
        }
      }, false);

stage.getContent().addEventListener('touchend', function() {
        lastDist = 0;
      }, false);

layer.add(triangle);
      layer.add(circle);
      stage.add(layer);

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

< Multi-Touch Shape Interactive Building Map >

More Examples

Modified on December 17th, 2012 by Eric Rowell