HTML5 Canvas Opacity Tutorial

To set a shape opacity with Konva, we can set the opacity property when we instantiate the node, 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.

If you want to apply transparency for several shapes without seen overlapping areas, take a look into Transparent Group Demo

Instructions: Mouseover the pentagon to change its opacity.

Konva Opacity Demoview raw

<!DOCTYPE html>
<html>
  <head>
    <script src="https://unpkg.com/[email protected]/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.width() / 2,
        y: stage.height() / 2,
        sides: 5,
        radius: 70,
        fill: 'red',
        stroke: 'black',
        strokeWidth: 4,
        opacity: 0.5,
      });

      pentagon.on('mouseover', function () {
        this.opacity(1);
      });

      pentagon.on('mouseout', function () {
        this.opacity(0.5);
      });

      // add the shape to the layer
      layer.add(pentagon);

      // add the layer to the stage
      stage.add(layer);
    </script>
  </body>
</html>

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