HTML5 Canvas Custom Filter Tutorial

How apply custom filter for Konva nodes?

This demo demonstrate how to use custom filters with Konva framework.

Filter is a function that have canvas ImageData as input and it should mutate it.

function Filter(imageData) {
  // do something with image data
  imageData.data[0] = 0;
}

For all available filters go to Filters Documentation.

Also take a look into Image Border Demo for custom filter example.

In this demo we will remove all transparency from the image..

Konva Custom Filter Image Demoview raw

<!DOCTYPE html>
<html>
  <head>
    <script src="https://unpkg.com/[email protected]/konva.min.js"></script>
    <meta charset="utf-8" />
    <title>Konva Custom Filter Demo</title>
    <style>
      body {
        margin: 0;
        padding: 0;
        overflow: hidden;
        background-color: #f0f0f0;
      }
    </style>
  </head>

  <body>
    <div id="container"></div>
    <script>
      var stage = new Konva.Stage({
        container: 'container',
        width: window.innerWidth,
        height: window.innerHeight,
      });

      var layer = new Konva.Layer();
      stage.add(layer);

      // lets define a custom filter:
      var OpacityFilter = function (imageData) {
        // make all pixels opaque 100%
        var nPixels = imageData.data.length;
        for (var i = 3; i < nPixels; i += 4) {
          imageData.data[i] = 255;
        }
      };

      Konva.Image.fromURL('/assets/lion.png', function (image) {
        layer.add(image);
        image.setAttrs({
          x: 80,
          y: 30,
          borderSize: 5,
          borderColor: 'red',
        });

        image.filters([OpacityFilter]);
        image.cache();
      });
    </script>
  </body>
</html>

Enjoying Konva? Please consider to support the project.