如何通过用户捕获图像's使用getUserMedia的网络摄像头

How can I capture an image via the user's webcam using getUserMedia?

本文关键字：使用 getUserMedia 摄像头 网络 用户 何通过 图像      更新时间：2023-09-26

我想在网上制作一个程序，通过用户的网络摄像头捕捉图像。

我正在使用getUserMedia Web API。这是我的代码，但它不起作用。如何更改它以捕获网络摄像头图像？

<div id="container">
    <video autoplay="true" id="videoElement">
    </video>
</div>
<script>
</script>

有JS:

var video = document.querySelector("#videoElement");
navigator.getUserMedia, elem = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia || navigator.oGetUserMedia;
console.log(navigator.getUserMedia);
if (navigator.getUserMedia) {
    navigator.getUserMedia({video: true}, handleVideo, videoError);
}
function handleVideo(stream) {
    video.src = window.URL.createObjectURL(stream);
}
function videoError(e) {
    // do something
}

您可以使用此工作样本

 <!DOCTYPE html>
<html>
  <head>
  </head>
  <body onload="init();">
    <h1>Take a snapshot of the current video stream</h1>
   Click on the Start WebCam button.
     <p>
    <button onclick="startWebcam();">Start WebCam</button>
    <button onclick="stopWebcam();">Stop WebCam</button> 
       <button onclick="snapshot();">Take Snapshot</button> 
    </p>
    <video onclick="snapshot(this);" width=400 height=400 id="video" controls autoplay></video>
  <p>
        Screenshots : <p>
      <canvas  id="myCanvas" width="400" height="350"></canvas>  
  </body>
  <script>
      //--------------------
      // GET USER MEDIA CODE
      //--------------------
          navigator.getUserMedia = ( navigator.getUserMedia ||
                             navigator.webkitGetUserMedia ||
                             navigator.mozGetUserMedia ||
                             navigator.msGetUserMedia);
      var video;
      var webcamStream;
            
      function startWebcam() {
        if (navigator.getUserMedia) {
           navigator.getUserMedia (
              // constraints
              {
                 video: true,
                 audio: false
              },
              // successCallback
              function(localMediaStream) {
                  video = document.querySelector('video');
                 video.srcObject=localMediaStream;
                 webcamStream = localMediaStream;
              },
              // errorCallback
              function(err) {
                 console.log("The following error occured: " + err);
              }
           );
        } else {
           console.log("getUserMedia not supported");
        }  
      }
            
      function stopWebcam() {
          webcamStream.stop();
      }
      //---------------------
      // TAKE A SNAPSHOT CODE
      //---------------------
      var canvas, ctx;
      function init() {
        // Get the canvas and obtain a context for
        // drawing in it
        canvas = document.getElementById("myCanvas");
        ctx = canvas.getContext('2d');
      }
      function snapshot() {
         // Draws current image from the video element into the canvas
        ctx.drawImage(video, 0,0, canvas.width, canvas.height);
      }
  </script>
</html>

getUserMedia api已经更新，现在公开了takePhoto和grabFrame。grabFrame方法不那么令人兴奋，因为它做了我们一直在做的事情，只是从流中返回下一个视频帧，但takePhoto会中断流，使用相机的"最高可用摄影相机分辨率"来捕捉压缩图像斑点。更多详细信息请点击此处：谷歌开发者

var stream, imageCapture; 
function getMediaStream()
{ 
    window.navigator.mediaDevices.getUserMedia({video: true})
    .then(function(mediaStream)
    { 
        stream = mediaStream; 
        let mediaStreamTrack = mediaStream.getVideoTracks()[0];
        imageCapture = new ImageCapture(mediaStreamTrack);
        console.log(imageCapture);
    })
    .catch(error);
}
function error(error)
{ 
    console.error('error:', error); 
}
function takePhoto(img)
{ 
    const img = img || document.querySelector('img');
    imageCapture.takePhoto()
    .then(blob => {
        let url = window.URL.createObjectURL(blob);
        img.src = url;
        window.URL.revokeObjectURL(url); 
    })
    .catch(error);
}; 
/* just call */ 
getMediaStream(); 
/* and when you want to capture an image */ 
takePhoto();

getUserMedia不受IE11支持，请查看此链接：https://caniuse.com/#search=getuserMedia

因此，如果您仍然想使用getUserMedia的核心属性，那么您需要使用polyfill。看看这个polyfillink：https://github.com/addyosmani/getUserMedia.js

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