canvas获取摄像头的图像

1、页面元素

<div id="contentHolder">
    <video id="video" width="320" height="320" autoplay>
    </video>
    <button id="snap"> 拍照</button>
    <canvas id="canvas" width="320" height="320">
    </canvas>
</div>

2、脚本方法

<script>
    var canvas = document.getElementById("canvas"),
            context = canvas.getContext("2d"),
            video = document.getElementById("video"),
            videoObj = {"video": true},
            errBack = function (error) {
                console.log("Video capture error: ", error.code);
            };
    //navigator.getUserMedia这个写法在Opera中好像是navigator.getUserMedianow
    if (navigator.getUserMedia) {
        navigator.getUserMedia(videoObj, function (stream) {
            video.src = stream;
            video.play();
        }, errBack);
    } else if (navigator.webkitGetUserMedia) {
        navigator.webkitGetUserMedia(videoObj, function (stream) {
            video.src = window.webkitURL.createObjectURL(stream);
            video.play();
        }, errBack);
    }
    //这个是拍照按钮的事件，
    $("#snap").click(function () {
        context.drawImage(video, 0, 0, 320, 320);
        video.pause();
    });
</script>

只支持chrome