HTML5 Canvas Stage Data URL Tutorial

To get the data URL of the stage with Konva, we can use the toDataURL()
method which requires a callback function for Stage (for other nodes callback is not required).
In addition, we can also pass in a mime type such as image/jpeg and a quality value that ranges between 0 and 1.
We can also get the data URLs of specific nodes, including layers, groups, and shapes.

Note: The toDataURL() method requires that any images drawn onto the canvas
are hosted on a web server with the same domain as the code executing it.
If this condition is not met, a SECURITY_ERR exception is thrown.

Instructions: Drag and drop the rectangle and then click on the save button to get the composite data url and open the resulting image in a new window

Konva Stage Data URL Demoview raw
<!DOCTYPE html>
<html>
<head>
<script src="https://cdn.rawgit.com/konvajs/konva/1.6.5/konva.min.js"></script>
<meta charset="utf-8">
<title>Konva Stage Data URL Demo</title>
<style>
body {
margin: 0;
padding: 0;
overflow: hidden;
background-color: #F0F0F0;
}
#buttons {
position: absolute;
top: 5px;
left: 10px;
}
#buttons>input {
padding: 10px;
display: block;
margin-top: 5px;
}
</style>
</head>
<body>
<div id="container"></div>
<div id="buttons">
<button id="save">
Save as image
</button>
</div>
<script>
var width = window.innerWidth;
var height = window.innerHeight;
var stage = new Konva.Stage({
container: 'container',
width: width,
height: height
});
var layer = new Konva.Layer();
var rectX = stage.getWidth() / 2 - 50;
var rectY = stage.getHeight() / 2 - 25;
var box = new Konva.Rect({
x: rectX,
y: rectY,
width: 100,
height: 50,
fill: '#00D2FF',
stroke: 'black',
strokeWidth: 4,
draggable: true
});
box.on('mouseover', function () {
document.body.style.cursor = 'pointer';
});
box.on('mouseout', function () {
document.body.style.cursor = 'default';
});
layer.add(box);
stage.add(layer);
// function from https://stackoverflow.com/a/15832662/512042
function downloadURI(uri, name) {
var link = document.createElement("a");
link.download = name;
link.href = uri;
document.body.appendChild(link);
link.click();
document.body.removeChild(link);
delete link;
}
document.getElementById('save').addEventListener('click', function () {
var dataURL = stage.toDataURL();
downloadURI(dataURL, 'stage.png');
}, false);
</script>
</body>
</html>