【转】Web调用电脑摄像头【实时画面、拍照、截图】

【原文】https://blog.csdn.net/qq_45021180/article/details/111561634

一、播放本地视频+截图

案例一代码：

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>demo01</title>
</head>

<body>
     <video id="myVideo" src="madashuai.mp4" loop="loop" autoplay="autoplay" controls="controls"></video><br>
     <button id="snapScreen">截屏</button>
     <canvas id="mycanvas" width="400" height="240"></canvas>
</body>

 <script>
   let mycanvas = document.getElementById('mycanvas').getContext('2d');
   let video = document.getElementById('myVideo');

   let snapScreen = document.getElementById('snapScreen');
   snapScreen.onclick = function () { // 按钮点击事件，将
     mycanvas.drawImage(video, 0, 0, 400, 240);
   }
 </script>

</html>

二、电脑摄像头的调用
实时显示画面

案例二代码：

<!doctype html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>摄像头调用2</title>
</head>

<body>
    <video id="v"></video>
</body>
<script>
    !(function () {
        // 老的浏览器可能根本没有实现 mediaDevices，所以我们可以先设置一个空的对象
        if (navigator.mediaDevices === undefined) {
            navigator.mediaDevices = {};
        }
        if (navigator.mediaDevices.getUserMedia === undefined) {
            navigator.mediaDevices.getUserMedia = function (constraints) {
                // 首先，如果有getUserMedia的话，就获得它
                var getUserMedia = navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;

                // 一些浏览器根本没实现它 - 那么就返回一个error到promise的reject来保持一个统一的接口
                if (!getUserMedia) {
                    return Promise.reject(new Error('getUserMedia is not implemented in this browser'));
                }

                // 否则，为老的navigator.getUserMedia方法包裹一个Promise
                return new Promise(function (resolve, reject) {
                    getUserMedia.call(navigator, constraints, resolve, reject);
                });
            }
        }
        const constraints = {
            video: true,
            audio: false
        };
        let promise = navigator.mediaDevices.getUserMedia(constraints);
        promise.then(stream => {
            let v = document.getElementById('v');
            // 旧的浏览器可能没有srcObject
            if ("srcObject" in v) {
                v.srcObject = stream;
            } else {
                // 防止再新的浏览器里使用它，应为它已经不再支持了
                v.src = window.URL.createObjectURL(stream);
            }
            v.onloadedmetadata = function (e) {
                v.play();
            };
        }).catch(err => {
            console.error(err.name + ": " + err.message);
        })
    })();
</script>
</html>

三、实时视频+拍照
初始画面：

拍照：

案例三代码：

<!doctype html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>拍照2</title>
</head>

<body>
    <button id="button_take">拍照</button><br />
    <div style="float: left;50%"><video id="v"></video></div>
    <canvas id="canvas" style="display:none;"></canvas><br />
    <img src="http://placehold.it/640&text=Your%20image%20here%20..." id="photo" alt="photo" style="float: left;">
</body>

<script>
    !(function () {
        // 老的浏览器可能根本没有实现 mediaDevices，所以我们可以先设置一个空的对象
        if (navigator.mediaDevices === undefined) {
            navigator.mediaDevices = {};
        }
        if (navigator.mediaDevices.getUserMedia === undefined) {
            navigator.mediaDevices.getUserMedia = function (constraints) {
                // 首先，如果有getUserMedia的话，就获得它
                var getUserMedia = navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;

                // 一些浏览器根本没实现它 - 那么就返回一个error到promise的reject来保持一个统一的接口
                if (!getUserMedia) {
                    return Promise.reject(new Error('getUserMedia is not implemented in this browser'));
                }

                // 否则，为老的navigator.getUserMedia方法包裹一个Promise
                return new Promise(function (resolve, reject) {
                    getUserMedia.call(navigator, constraints, resolve, reject);
                });
            }
        }
        const constraints = {
            video: true,
            audio: false
        };
        let videoPlaying = false;
        let v = document.getElementById('v');
        let promise = navigator.mediaDevices.getUserMedia(constraints);
        promise.then(stream => {
            // 旧的浏览器可能没有srcObject
            if ("srcObject" in v) {
                v.srcObject = stream;
            } else {
                // 防止再新的浏览器里使用它，应为它已经不再支持了
                v.src = window.URL.createObjectURL(stream);
            }
            v.onloadedmetadata = function (e) {
                v.play();
                videoPlaying = true;
            };
        }).catch(err => {
            console.error(err.name + ": " + err.message);
        });
        document.getElementById('button_take').addEventListener('click', function () {
            if (videoPlaying) {
                let canvas = document.getElementById('canvas');
                canvas.width = v.videoWidth;
                canvas.height = v.videoHeight;
                canvas.getContext('2d').drawImage(v, 0, 0);
                let data = canvas.toDataURL('image/webp');
                document.getElementById('photo').setAttribute('src', data);
                //   canvas.getContext("2d").drawImage(Img,0,0,width,height); //将图片绘制到canvas中
            }
        }, false);
    })();
</script>
</html>

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原文链接：https://blog.csdn.net/qq_45021180/article/details/111561634