PaintWorklet

The PaintWorklet interface of the CSS Painting API programmatically generates an image where a CSS property expects a file. Access this interface through CSS.paintWorklet.

Properties

PaintWorklet.devicePixelRatio
Returns the current device's ratio of physical pixels to logical pixels.

Event handlers

None.

Methods

This interface inherits methods from Worklet.

PaintWorklet.registerPaint()
Registers a class programmatically generate an image where a CSS property expects a file.
PaintWorklet.addModule()
The addModule() method, inhertied from the Worklet interface loads the module in the given JavaScript file and adds it to the current PaintWorklet.

Examples

The following three example go together showing creating, loading, and using a PaintWorklet.

Create a PaintWorklet

The following shows an example worklet module. This should be in a separate js file. Note that registerPaint() is called without a reference to PaintWorklet.

class CheckerboardPainter {
  paint(ctx, geom, properties) {
    // Use `ctx` as if it was a normal canvas
    const colors = ['red', 'green', 'blue'];
    const size = 32;
    for(let y = 0; y < geom.height/size; y++) {
      for(let x = 0; x < geom.width/size; x++) {
        const color = colors[(x + y) % colors.length];
        ctx.beginPath();
        ctx.fillStyle = color;
        ctx.rect(x * size, y * size, size, size);
        ctx.fill();
      }
    }
  }
}

// Register our class under a specific name
registerPaint('checkerboard', CheckerboardPainter);

Load a PaintWorklet

The following example demonstrates loading the above worklet from its js file and does so by feature detection.

<script>
  if ('paintWorklet' in CSS) {
    CSS.paintWorklet.addModule('checkerboard.js');
  }
</script>

Use a PaintWorklet

This example shows how to use a PaintWorklet in a stylesheet, including the simplest way to provide a fallback if PaintWorklet isn't supported. 

<style>
  textarea {
    background-image: url(checkerboard);
    background-image: paint(checkerboard);
  }
</style>
<textarea></textarea>

You can also use the @supports at-rule.

@supports (background: paint(id)) {
  background-image: paint(checkerboard);
}

Specifications

Specification Status Comment
CSS Painting API Level 1
The definition of 'PaintWorkletGlobalScope' in that specification.
Working Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
PaintWorkletGlobalScopeChrome Full support 65Edge ? Firefox ? IE No support NoOpera ? Safari ? WebView Android Full support 65Chrome Android Full support 65Edge Mobile ? Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android ?
devicePixelRatioChrome Full support 65Edge ? Firefox ? IE No support NoOpera ? Safari ? WebView Android Full support 65Chrome Android Full support 65Edge Mobile ? Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android ?
registerPaintChrome Full support 65Edge ? Firefox ? IE No support NoOpera ? Safari ? WebView Android Full support 65Chrome Android Full support 65Edge Mobile ? Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown

 

See Also

 

Document Tags and Contributors

Contributors to this page: estelle, Puddingsan, jpmedley
Last updated by: estelle,