ImageCapture: grabFrame() method

The grabFrame() method of the ImageCapture interface takes a snapshot of the live video in a MediaStreamTrack and returns a Promise that resolves with an ImageBitmap containing the snapshot.

Syntax

grabFrame()

Parameters

None.

Return value

A Promise that resolves to an ImageBitmap object.

Exceptions

• InvalidStateError DOMException
  • : Thrown if readyState property of the MediaStreamTrack passing in the constructor is not live.
• UnknownError DOMException
  • : Thrown if the operation can’t complete for any reason.

Examples

This example is extracted from this Simple Image Capture demo. It shows how to use the Promise returned by grabFrame() to copy the returned frame to a <canvas> element. For simplicity it does not show how to instantiate the ImageCapture object.

let grabFrameButton = document.querySelector("button#grabFrame");
let canvas = document.querySelector("canvas");

grabFrameButton.onclick = grabFrame;

function grabFrame() {
  imageCapture
    .grabFrame()
    .then((imageBitmap) => {
      console.log("Grabbed frame:", imageBitmap);
      canvas.width = imageBitmap.width;
      canvas.height = imageBitmap.height;
      canvas.getContext("2d").drawImage(imageBitmap, 0, 0);
      canvas.classList.remove("hidden");
    })
    .catch((error) => {
      console.error("grabFrame() error: ", error);
    });
}

Specifications

Browser compatibility