详解HTML5 使用video标签实现选择摄像头功能

详解HTML5 使用video标签实现选择摄像头功能

1. html

// jquery reference
// <script src="http://ajax.googleapis.com/ajax/libs/jquery/2.0.2/jquery.min.js"></script>
// 

  <input type="hidden" name="imgValue" id="imgValue" />
  <button id="btnOpen1" class="btn btn-default" type="button" >Open WebCam</button>
  <select id="videoSource" ></select> 

  <div id="vdoOne" style="display:none">
    <video id="video" style="margin-top:15px;margin-bottom:15px;" width="300" autoplay></video>
    <canvas id="canvasPreview" style="margin-top:15px;" width="300" height="224"></canvas>
    <canvas id="canvasUpload" style="display:none;" width='300' height='224'></canvas>
    <button id="snap" class="btn btn-default" type="button">Snap Photo</button>
  </div>

2. javascript

<script> 

//// Elements for taking the snapshot
    var canvasPreview = document.getElementById('canvasPreview');
    var canvasUpload = document.getElementById('canvasUpload');
    var contextPreview = canvasPreview.getContext('2d');
    var contextUpload = canvasUpload.getContext('2d'); 

    //#################### Video Source #######################3
    var videoElement = document.querySelector('video');
    var videoSelect = document.querySelector('select#videoSource'); 

    navigator.mediaDevices.enumerateDevices()
      .then(gotDevices).then(getStream).catch(handleError); 

    videoSelect.onchange = getStream; 

    function gotDevices(deviceInfos) {
      for (var i = 0; i < deviceInfos.length; ++i) {
        var deviceInfo = deviceInfos[i];
        var option = document.createElement('option');
        option.value = deviceInfo.deviceId;
        if (deviceInfo.kind === 'videoinput') {
          option.text = deviceInfo.label ||
            'camera ' +
            (videoSelect.length + 1);
          videoSelect.appendChild(option);
        } else {
          console.log('Found ome other kind of source/device: ', deviceInfo);
        }
      }
    } 

    var _streamCopy = null;
    function getStream() {
      if (_streamCopy != null) {
        try {
          _streamCopy.stop(); // if this method doesn't exist, the catch will be executed.
        } catch (e) {
          _streamCopy.getVideoTracks()[0].stop(); // then stop the first video track of the stream
        }
      } 

      var constraints = {
        audio:false,
        video: {
          optional: [
            {
              sourceId: videoSelect.value
            }
          ]
        }
      }; 

      navigator.mediaDevices.getUserMedia(constraints).then(gotStream).catch(handleError);
    } 

    function gotStream(stream) {
      _streamCopy = stream; // make stream available to console
      videoElement.srcObject = stream;
    } 

    function handleError(error) {
      alert(error.name + ": " + error.message);
    } 

    //######################## End Video Source ################# 

    // Get access to the camera!
    if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
      navigator.mediaDevices.getUserMedia({ video: true }).then(function(stream) {
        videoElement.src = window.URL.createObjectURL(stream);
        videoElement.play(); 

      });
    } else {
      document.getElementById("pnlVideo1").style.display = "none";
    } 

    //// Trigger photo take
    document.getElementById("snap").addEventListener("click",
      function() {
        contextPreview.drawImage(videoElement, 0, 0, 300, 224);
        contextUpload.drawImage(videoElement, 0, 0, 300, 224);
        document.getElementById("video").style.display = "none";
        document.getElementById("snap").style.display = "none";
        document.getElementById("canvasPreview").style.display = "block"; 

        var image = document.getElementById("canvasUpload").toDataURL("image/jpeg");
        image = image.replace('data:image/jpeg;base64,', '');
        $("#imgValue").val(image); 

        alert("image value :" + image);
      }); 

    //// Trigger photo take 

    document.getElementById("btnOpen1").addEventListener("click",
      function() {
        document.getElementById("vdoOne").style.display = "block";
        document.getElementById("video").style.display = "block";
        document.getElementById("snap").style.display = "block";
        document.getElementById("canvasPreview").style.display = "none";
      }); 

</script>

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