照相拍照功能

https://whatwebcando.today/photos.html

function getUserMedia(options, successCallback, failureCallback) {
  var api = navigator.getUserMedia || navigator.webkitGetUserMedia ||
    navigator.mozGetUserMedia || navigator.msGetUserMedia;
  if (api) {
    return api.bind(navigator)(options, successCallback, failureCallback);
  }
}

var theStream;

function getStream() {
  if (!navigator.getUserMedia && !navigator.webkitGetUserMedia &&
    !navigator.mozGetUserMedia && !navigator.msGetUserMedia) {
    alert('User Media API not supported.');
    return;
  }
  
  var constraints = {
    video: true
  };

  getUserMedia(constraints, function (stream) {
    var mediaControl = document.querySelector('video');
    if ('srcObject' in mediaControl) {
      mediaControl.srcObject = stream;
    } else if (navigator.mozGetUserMedia) {
      mediaControl.mozSrcObject = stream;
    } else {
      mediaControl.src = (window.URL || window.webkitURL).createObjectURL(stream);
    }
    theStream = stream;
  }, function (err) {
    alert('Error: ' + err);
  });
}

function takePhoto() {
  if (!('ImageCapture' in window)) {
    alert('ImageCapture is not available');
    return;
  }
  
  if (!theStream) {
    alert('Grab the video stream first!');
    return;
  }
  
  var theImageCapturer = new ImageCapture(theStream.getVideoTracks()[0]);

  theImageCapturer.takePhoto()
    .then(blob => {
      var theImageTag = document.getElementById("imageTag");
      theImageTag.src = URL.createObjectURL(blob);
    })
    .catch(err => alert('Error: ' + err));

MediaDevices.getUserMedia undefined 的问题

MediaDevices.getUserMedia只工作于以下三种环境：

• localhost 域
• 开启了 HTTPS 的域
• 使用 file:/// 协议打开的本地文件

如果暂时没有完成https，可以使用以下方法
chrome://flags/#unsafely-treat-insecure-origin-as-secure
--unsafely-treat-insecure-origin-as-secure="http://example.com"