How to access image frames in a webcam using javascript

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I want to make a live face recognition system. My code so far detects a human face. I want to be able to process or scan the frames in the webcam to recognize the faces. I am using getUserMedia to load the webcam. I want to make the recognition process live instead of having to store the image for recognition. Following is the code I am using to start the webcam. I am a beginner so sorry for any confusions, any help is appreciated. Thank you!

    function startVideo() {
  document.body.append('Loaded')
  navigator.getUserMedia(
    { video: {} },
    stream => video.srcObject = stream,
    err => console.error(err)
  )
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2 Answers

You didn't what format you want for your webcam-captured images to be delivered. It's pretty easy to deliver them into a <canvas /> element.

  • You use gUM to open up a video stream, then
  • preview it in a <video /> element, then
  • use drawImage to copy a snapshot of that element to your canvas.

Here's some example code, based on the "official" webrtc sample.

Initialize

const video = document.querySelector('video');
const canvas = document.querySelector('canvas');
canvas.width = 480;
canvas.height = 360;
const button = document.querySelector('button');

Snapshot button click handler

See the drawImage() method call... that's what grabs the snap of the video preview element.

button.onclick = function() {
  /* set the canvas to the dimensions of the video feed */
  canvas.width = video.videoWidth;
  canvas.height = video.videoHeight;
  /* make the snapshot */
  canvas.getContext('2d').drawImage(video, 0, 0, canvas.width, canvas.height);
};

Start and preview the video stream

navigator.mediaDevices.getUserMedia( {audio: false, video: true })
.then(stream => video.srcObject = stream)
.catch(error => console.error(error);

Obviously this is very simple. The parameter you pass to gUM is a MediaStreamConstraints object. It gives you a lot of control over the video (and audio) you want to capture.

user_2056080

HTML

<center><video id="video" width="640" height="480" autoplay></video></center>

JavaScript

var video = document.getElementById('video');
if(navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
 navigator.mediaDevices.getUserMedia({ video: true }).then(function(stream) {
 video.src = window.URL.createObjectURL(stream);
 video.play();
 });
}
user_76581190
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