js+HTML5基于过滤器从摄像头中捕获视频的方法

<div class="warning"><h2>Native web camera streaming (getUserMedia) is not supported in this browser.</h2></div><div class="container">  <h3>Current filter is: None</h3>  <button>Click here to change video filter</button>  <div style="clear:both"></div>  <div class="col">    <h2>HTML5 <video> object</h2>    <video></video>  </div>  <div class="col">    <h2>HTML5 <canvas> object</h2>    <canvas width="600" height="450"></canvas>  </div></div>

.grayscale{  -webkit-filter:grayscale(1);  -moz-filter:grayscale(1);  -o-filter:grayscale(1);  -ms-filter:grayscale(1);  filter:grayscale(1);}.sepia{  -webkit-filter:sepia(0.8);  -moz-filter:sepia(0.8);  -o-filter:sepia(0.8);  -ms-filter:sepia(0.8);  filter:sepia(0.8);}.blur{  -webkit-filter:blur(3px);  -moz-filter:blur(3px);  -o-filter:blur(3px);  -ms-filter:blur(3px);  filter:blur(3px);}.brightness{  -webkit-filter:brightness(0.3);  -moz-filter:brightness(0.3);  -o-filter:brightness(0.3);  -ms-filter:brightness(0.3);  filter:brightness(0.3);}.contrast{  -webkit-filter:contrast(0.5);  -moz-filter:contrast(0.5);  -o-filter:contrast(0.5);  -ms-filter:contrast(0.5);  filter:contrast(0.5);}.hue-rotate{  -webkit-filter:hue-rotate(90deg);  -moz-filter:hue-rotate(90deg);  -o-filter:hue-rotate(90deg);  -ms-filter:hue-rotate(90deg);  filter:hue-rotate(90deg);}.hue-rotate2{  -webkit-filter:hue-rotate(180deg);  -moz-filter:hue-rotate(180deg);  -o-filter:hue-rotate(180deg);  -ms-filter:hue-rotate(180deg);  filter:hue-rotate(180deg);}.hue-rotate3{  -webkit-filter:hue-rotate(270deg);  -moz-filter:hue-rotate(270deg);  -o-filter:hue-rotate(270deg);  -ms-filter:hue-rotate(270deg);  filter:hue-rotate(270deg);}.saturate{  -webkit-filter:saturate(10);  -moz-filter:saturate(10);  -o-filter:saturate(10);  -ms-filter:saturate(10);  filter:saturate(10);}.invert{  -webkit-filter:invert(1);  -moz-filter:invert(1);  -o-filter: invert(1);  -ms-filter: invert(1);  filter: invert(1);}

// Main initializationdocument.addEventListener('DOMContentLoaded', function() {  // Global variables  var video = document.querySelector('video');  var audio, audioType;  var canvas = document.querySelector('canvas');  var context = canvas.getContext('2d');  // Custom video filters  var iFilter = 0;  var filters = [    'grayscale',    'sepia',    'blur',    'brightness',    'contrast',    'hue-rotate',    'hue-rotate2',    'hue-rotate3',    'saturate',    'invert',    'none'  ];  // Get the video stream from the camera with getUserMedia  navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia ||    navigator.mozGetUserMedia || navigator.msGetUserMedia;  window.URL = window.URL || window.webkitURL || window.mozURL || window.msURL;  if (navigator.getUserMedia) {    // Evoke getUserMedia function    navigator.getUserMedia({video: true, audio: true}, onSuccessCallback, onErrorCallback);    function onSuccessCallback(stream) {      // Use the stream from the camera as the source of the video element      video.src = window.URL.createObjectURL(stream) || stream;      // Autoplay      video.play();      // HTML5 Audio      audio = new Audio();      audioType = getAudioType(audio);      if (audioType) {        audio.src = 'polaroid.' + audioType;        audio.play();      }    }    // Display an error    function onErrorCallback(e) {      var expl = 'An error occurred: [Reason: ' + e.code + ']';      console.error(expl);      alert(expl);      return;    }  } else {    document.querySelector('.container').style.visibility = 'hidden';    document.querySelector('.warning').style.visibility = 'visible';    return;  }  // Draw the video stream at the canvas object  function drawVideoAtCanvas(obj, context) {    window.setInterval(function() {      context.drawImage(obj, 0, 0);    }, 60);  }  // The canPlayType() function doesn't return true or false. In recognition of how complex  // formats are, the function returns a string: 'probably', 'maybe' or an empty string.  function getAudioType(element) {    if (element.canPlayType) {      if (element.canPlayType('audio/mp4; codecs="mp4a.40.5"') !== '') {        return('aac');      } else if (element.canPlayType('audio/ogg; codecs="vorbis"') !== '') {        return("ogg");      }    }    return false;  }  // Add event listener for our video's Play function in order to produce video at the canvas  video.addEventListener('play', function() {    drawVideoAtCanvas(this, context);  }, false);  // Add event listener for our Button (to switch video filters)  document.querySelector('button').addEventListener('click', function() {    video.className = '';    canvas.className = '';    var effect = filters[iFilter++ % filters.length]; // Loop through the filters.    if (effect) {      video.classList.add(effect);      canvas.classList.add(effect);      document.querySelector('.container h3').innerHTML = 'Current filter is: ' + effect;    }  }, false);}, false);