Html5调用摄像头功能的实现代码有什么?

Html5调用摄像头功能的实现代码有什么?

前言

前些天,线上笔试的时候,发现需要浏览器同意开启摄像头,感觉像是 js 调用的,由于当时笔试,也就没想到这么多问题。今天闲来无事,看了下自己的 todo,发现有这个调用摄像头的todo,才想到😂。网上查了一下,果然 js 有调用摄像头的 api,为此自己写一个 demo ,避免忘记。

正文

调用摄像头

一共有两种实现方式,一种是使用navigator.getUserMedia(该特性已经从 Web 标准中删除,虽然一些浏览器目前仍然支持它,但也许会在未来的某个时间停止支持,请尽量不要使用该特性),前面一种已经从 Web 标准中删除,仅为了向后兼容而存在,第二种是使用navigator.mediaDevices.getUserMedia(推荐使用),这两种方法 Safari 貌似都不支持。。。。

第一种方法navigator.getUserMedia用法详见mdn ,代码如下:

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>摄像头调用1</title>
</head>
<body>
  <video id="v"></video>
  <script>
    !(function () {
      function userMedia() {
        return navigator.getUserMedia = navigator.getUserMedia ||
          navigator.webkitGetUserMedia ||
          navigator.mozGetUserMedia ||
          navigator.msGetUserMedia || null;
      }
      if (userMedia()) {
        var constraints = {
          video: true,
          audio: false
        };
        var media = navigator.getUserMedia(constraints, function (stream) {
          var v = document.getElementById('v');
          var url = window.URL || window.webkitURL;
          v.src = url ? url.createObjectURL(stream) : stream;
          v.play();
        }, function (error) {
          console.log("ERROR");
          console.log(error);
        });
      } else {
        console.log("不支持");
      }
    })();
  </script>
</body>
</html>

第二种方法navigator.mediaDevices.getUserMedia用法详见mdn。navigator.mediaDevices.getUserMedia 其实和第一种差不多,主要第二种返回是一个 Promise 对象,代码如下:

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>摄像头调用2</title>
</head>
<body>
  <video id="v"></video>
  <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>
</body>
</html>

拍照

思路是设置一个标志变量 videoPlaying 看看是否 video 有在 play,监听拍照按钮的点击事件,如果videoPlaying 为 true ,使用一个canvas 获取 video 的宽高(默认 canvas 是不显示的),然后使用 canvas 的drawImage,然后使用 canvas 的 toDataURL返回一个 data url,将这个 url,设置在一个 img 标签上即可😀

第一种方法navigator.getUserMedia实现代码:

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>拍照1</title>
</head>
<body>
  <button id="take">拍照</button>
  <br />
  <video id="v" style="width: 640px;height: 480px;"></video>
  <canvas id="canvas" style="display:none;"></canvas>
  <br />
  <img src="http://placehold.it/640&text=Your%20image%20here%20..." id="photo" alt="photo">
  <script>
    !(function () {
      function userMedia() {
        return navigator.getUserMedia = navigator.getUserMedia ||
          navigator.webkitGetUserMedia ||
          navigator.mozGetUserMedia ||
          navigator.msGetUserMedia || null;
      }
      if (userMedia()) {
        let videoPlaying = false;
        let constraints = {
          video: true,
          audio: false
        };
        let video = document.getElementById('v');
        let media = navigator.getUserMedia(constraints, function (stream) {
          let url = window.URL || window.webkitURL;
          video.src = url ? url.createObjectURL(stream) : stream;
          video.play();
          videoPlaying = true;
        }, function (error) {
          console.log("ERROR");
          console.log(error);
        });
        document.getElementById('take').addEventListener('click', function () {
          if (videoPlaying) {
            let canvas = document.getElementById('canvas');
            canvas.width = video.videoWidth;
            canvas.height = video.videoHeight;
            canvas.getContext('2d').drawImage(video, 0, 0);
            let data = canvas.toDataURL('image/webp');
            document.getElementById('photo').setAttribute('src', data);
          }
        }, false);
      } else {
        console.log("不支持");
      }
    })();
  </script>
</body>
</html>

第二种navigator.mediaDevices.getUserMedia实现方法:

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>拍照2</title>
</head>

<body>
  <button id="take">拍照</button>
  <br />
  <video id="v" style="width: 640px;height: 480px;"></video>
  <canvas id="canvas" style="display:none;"></canvas>
  <br />
  <img src="http://placehold.it/640&text=Your%20image%20here%20..." id="photo" alt="photo">
  <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('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);
        }
      }, false);
    })();
  </script>
</body>
</html>

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持路饭。