navigator调用摄像头pc

navigator 调取摄像头

async　　异步请求方式
await 　 等待Promise请求完成

//开启摄像头
async function startCamera() {
    let video = document.getElementById("video");
    let stream = await navigator.mediaDevices.getUserMedia({
        video: {
            width:100,
            height: 200
        },
        audio: false
    })
    video.srcObject = stream;
    video.play();
}

//关闭摄像头

function closeCamera(){
    let stream = document.getElementById('video').srcObject;
    let tracks = stream.getTracks();
    tracks.forEach(function(track) {
        track.stop();
    });
    document.getElementById('video').srcObject = null;
}

//拍照
function takephoto(){
  let video = document.getElementById('video');//视频标签
  let canvas = document.getElementById('outputCanvas');//
  let ctx = canvas.getContext('2d');//设置格式
  ctx.drawImage(video, 0, 0,640,480);       
  let img = document.getElementById('outputCanvas').toDataURL();//图片 base64格式可直接做img
}