JavaScript如何调用摄像头

如何使用浏览器调用摄像头

在JavaScript中使用浏览器调用摄像头会使用到以下方法:navigator.getUserMedia({video:true,audio:false},success,error)
参数1:是一个对象包含摄像头和麦克风{video:true,audio:false}
true表示开启,false表示关闭
参数2:调用成功回调success
参数3:调用失败回调error

需求:

  1. 调用摄像头和麦克风
  2. video视频标签显示摄像头图像
  3. 将摄像头捕获的图像放置在页面canvas标签

实现:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <style>
        video{
            width: 300px;
            height: 300px;
            border: 1px solid #ccc;
        }
        canvas{
            width: 300px;
            height: 300px;
            border: 1px solid red;
        }
    </style>
    <title>Document</title>
</head>
<body>
    <video autoplay id='video'></video>
    <canvas id="output"></canvas>
</body>
</html>
<script>
    //var video = document.getElementById('video')
    //var back = document.getElementById('output')
    var video = $("#video").get(0)
    var back = $("#output").get(0)
    //console.log(back,video)
    var backcontext = back.getContext('2d')
    function draw() {
        backcontext.drawImage(video,0,0,back.width,back.height)
        try{
            backcontext.drawImage(video,0,0,back.width,back.height)
        }catch(e){
            if(e.name == "NS_ERROR_NOT_AVAILABLE"){
                return setInterval(draw,200)
            }else{
                throw e
            }
        }
        setTimeout(draw,200)
    }
    var success = function(stream){
        console.log('摄像头开启成功')
        //videoUrl = window.URL.createObjectURL(stream)
        //video.src = videoUrl
		video.srcObject = stream
        draw()
    }
    var error = (error)=>{
        alert('调用失败')
    }
    navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia
    navigator.getUserMedia({video:true,audio:false},success,error)
</script>

效果图:
JavaScript如何调用摄像头_第1张图片

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