js调用手机相机并获取照片

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<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">
    <meta name="author" content="GaryWang">
    <meta name='renderer' content='webkit'>
    <meta http-equiv='X-UA-Compatible' content='IE=Edge,chrome=1' >
    <meta name="apple-mobile-web-app-capable" content="yes">
    <meta name="apple-mobile-web-app-status-bar-style" content="black">
    <meta name="format-detection" content="telephone=no">
    <meta name="format-detection" content="email=no">
    <title></title>
    <link href="css/basic.css" rel="stylesheet" type="text/css" />
    <link href="css/toast.css" rel="stylesheet" type="text/css" />
    <script>
        function autoScale(){
            var winW = document.documentElement.clientWidth;
            return Math.min (1,Math.min(winW / 750));
        }
        document.documentElement.style.cssText = 'font-size:'+(100 * autoScale())+'px';
        //1rem = 100px
    </script>
</head>
<body>
    <div class="wrap">
        <div class="shadow">
            <div class="btn"></div>
        </div>
        <video src="" id="videoElement" loop preload style="margin:0 auto;"></video>
        <canvas id="canvas"></canvas>
    </div>
    <script src="js/jquery-1.11.3.min.js"></script>
    <script>
        const [w,h] = [600,600]   //设置调用相机大小canvas宽高 drawimage的宽高
        var video = document.getElementById("videoElement");
        setTimeout(() => {
            if (
            navigator.mediaDevices.getUserMedia ||
            navigator.getUserMedia ||
            navigator.webkitGetUserMedia ||
            navigator.mozGetUserMedia
            ) {
            //调用用户媒体设备, 访问摄像头
            getUserMedia(
                {
                    video: {
                        width:w,
                        height:h
                    }
                },
                function videoSuccess(stream) {
                    mediaStreamTrack = stream;
                    video.srcObject = stream;
                    video.play();
                },
                function videoError(error) {
                    alert("摄像头打开失败,请检查权限设置!");
                }
            );
            } else {
                alert("摄像头打开失败,请检查权限设置!");
            }
      }, 500);

    function getUserMedia(constraints, success, error) {
      if (navigator.mediaDevices.getUserMedia) {
        //最新的标准API
        navigator.mediaDevices
          .getUserMedia(constraints)
          .then(success)
          .catch(error);
      } else if (navigator.webkitGetUserMedia) {
        //webkit核心浏览器
        navigator.webkitGetUserMedia(constraints, success, error);
      } else if (navigator.mozGetUserMedia) {
        //firfox浏览器
        navigator.mozGetUserMedia(constraints, success, error);
      } else if (navigator.getUserMedia) {
        //旧版API
        navigator.getUserMedia(constraints, success, error);
      }
    }
    //点击按钮后在canvas中绘制视频流并导出图片
    $('.btn').click(function(){
        var canvas = document.createElement("canvas");
        canvas.width = w; 
        canvas.height = h; 
        let context = canvas.getContext("2d");
        context.drawImage(video, 0, 0,w, h);
        context.scale(-1, 1); //水平翻转照片
        var imgSrc = canvas.toDataURL("image/png");
        $('.shadow').append(
            `<img src=${imgSrc} />`
        )
    })

    </script>
</body>
</html>