HTML5 Canvas Opacity Tutorial

To set a shape opacity with Konva, we can set the opacity property when we instantiate the shape, or we can use the opacity() method.

Shapes can have an opacity value between 0 and 1, where 0 is fully transparent, and 1 is fully opaque. Unless otherwise specified, all shapes are defaulted with an opacity value of 1.

Instructions: Mouseover the pentagon to change its opacity.

Konva Opacity Demoview raw
<!DOCTYPE html>
<html>
<head>
<script src="https://cdn.rawgit.com/konvajs/konva/1.7.2/konva.min.js"></script>
<meta charset="utf-8">
<title>Konva Opacity 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
});
var layer = new Konva.Layer();
var pentagon = new Konva.RegularPolygon({
x: stage.getWidth() / 2,
y: stage.getHeight() / 2,
sides: 5,
radius: 70,
fill: 'red',
stroke: 'black',
strokeWidth: 4,
opacity: 0.5
});
pentagon.on('mouseover', function() {
this.opacity(1);
layer.draw();
});
pentagon.on('mouseout', function() {
this.opacity(0.5);
layer.draw();
});
// add the shape to the layer
layer.add(pentagon);
// add the layer to the stage
stage.add(layer);
</script>
</body>
</html>