详解HTML5 使用video标签实现选择摄像头功能

// 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> 


  

<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>