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How to Export an HTML5 Canvas as an Image

The browser can encode a canvas as a data URL or a Blob. Konva provides toDataURL() and toBlob() on stages and nodes.

Use toBlob() for large exports when the browser supports it. A Blob does not create the large encoded string that a data URL creates.

Export a Konva stage from React​

This example exports the stage as a PNG. The pixelRatio value doubles each output dimension.

import { useRef } from 'react';
import { Stage, Layer, Rect, Circle, Text } from 'react-konva';

const App = () => {
  const stageRef = useRef(null);

  const downloadImage = () => {
    const dataUrl = stageRef.current.toDataURL({ pixelRatio: 2 });
    const link = document.createElement('a');
    link.download = 'konva-scene.png';
    link.href = dataUrl;
    document.body.appendChild(link);
    link.click();
    link.remove();
  };

  return (
    <>
      <button onClick={downloadImage}>Download PNG</button>
      <Stage ref={stageRef} width={Math.min(window.innerWidth, 760)} height={360}>
        <Layer>
          <Rect width={760} height={360} fill="#e7f5ff" />
          <Text
            x={30}
            y={28}
            text="Export this scene"
            fontSize={30}
            fill="#1864ab"
          />
          <Circle x={180} y={190} radius={70} fill="#4dabf7" />
          <Rect
            x={330}
            y={120}
            width={220}
            height={140}
            fill="#ffd43b"
            cornerRadius={16}
          />
        </Layer>
      </Stage>
    </>
  );
};

export default App;

The export includes only canvas content. HTML controls above the stage are not part of the image.

Set the file type and area​

Pass mimeType: 'image/jpeg' for JPEG output. JPEG has no transparency, so add a background shape before the other scene content.

Pass x, y, width, and height to export part of a stage. Pass pixelRatio to increase the resolution without changing scene coordinates.

High pixel ratios use more memory. A 2× ratio creates four times as many output pixels. Use the smallest ratio that meets the output requirement.

Prevent a tainted canvas​

The browser blocks export after Canvas draws an image without permitted cross-origin access. The image server must return a suitable Access-Control-Allow-Origin header. Load the image with crossOrigin set before its src value.

Read the tainted canvas guide for complete image-loading examples. Read high-quality export for more resolution details.