<!--video用于顯示媒體設備的視頻流，自動播放-->   
<video  id="video" autoplay style="width: 480px;height: 320px"></video>
<!--拍照按鈕-->
<div>
    <button id="capture">拍照</button>
</div>
<!--描繪video截圖-->
<canvas id="canvas" width="480" height="320"></canvas>

<script>  
    var video = document.getElementById('video');
    var canvas = document.getElementById('canvas');
    var capture = document.getElementById('capture');
    var context = canvas.getContext('2d');
    function getUserMediaToPhoto(constraints,success,error) {
        if(navigator.mediaDevices.getUserMedia){
            //最新標準API
            navigator.mediaDevices.getUserMedia(constraints).then(success).catch(error);
        }else if (navigator.webkitGetUserMedia) {
            //webkit核心瀏覽器
            navigator.webkitGetUserMedia(constraints,success,error);
        }else if(navigator.mozGetUserMedia){
            //firefox瀏覽器
            navigator.mozGetUserMedia(constraints,success,error);
        }else if(navigator.getUserMedia){
            //舊版API
            navigator.getUserMedia(constraints,success,error);
        }
    }
    //成功回調函數
    function success(stream){
        //兼容webkit核心瀏覽器
        var CompatibleURL = window.URL || window.webkitURL;
        //將視頻流轉化為video的源
        video.src = CompatibleURL.createObjectURL(stream);
        video.play();//播放視頻
    }
    function error(error) {
        console.log('訪問用戶媒體失敗：',error.name,error.message);
    }
    if(navigator.mediaDevices.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.getUserMedia){
        getUserMediaToPhoto({video:{width:480,height:320}},success,error);
    }else{
        alert('你的瀏覽器不支持訪問用戶媒體設備');
    }
    capture.addEventListener('click',function() {
        // 將video畫面描繪在canvas畫布上
        context.drawImage(video,0,0,480,320);
    })
 </script>