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ImageCapture.grabFrame() - Web APIs 编辑

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

Syntax

const bitmapPromise = imageCapture.grabFrame()

Return value

A Promise that resolves to an ImageBitmap object.

Example

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 simplicy it does not show how to instantiate the ImageCapture object.

var grabFrameButton = document.querySelector('button#grabFrame');
var canvas = document.querySelector('canvas');

grabFrameButton.onclick = grabFrame;

function grabFrame() {
  imageCapture.grabFrame()
  .then(function(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(function(error) {
    console.log('grabFrame() error: ', error);
  });
}