Multi-touch Scale Stage

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

Konva Multi-touch Scale Stageview raw
<!DOCTYPE html>
<html>
<head>
<script src="https://cdn.rawgit.com/konvajs/konva/1.5.0/konva.min.js"></script>
<meta charset="utf-8">
<title>Konva Multi-touch Scale Stage 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 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 Konva.Stage({
container: 'container',
width: width,
height: height,
draggable: true,
x: width / 2,
y: height / 2,
offset: {
x : width / 2,
y : height / 2
}
});
var layer = new Konva.Layer();
var triangle = new Konva.RegularPolygon({
x: 190,
y: stage.getHeight() / 2,
sides: 3,
radius: 80,
fill: 'green',
stroke: 'black',
strokeWidth: 4
});
var circle = new Konva.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.getScaleX() * dist / lastDist;
stage.scaleX(scale);
stage.scaleY(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>