js和HTML5基于过滤器从摄像头中捕获视频的方法

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

.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 initialization
document.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);