javascript - 将绘制的画布保存到每个间隔的文件

Question

下面是 HTML 和 JS 代码的一部分，它尝试在某个定义的时间间隔内从网络摄像头捕获图片并将其保存为服务器上的单独文件：

<video id="player" controls autoplay></video>
<canvas id="canvas" width=320 height=240></canvas>
<script>
const player = document.getElementById('player');
const canvas = document.getElementById('canvas');
const context = canvas.getContext('2d');
const captureButton = document.getElementById('capture');
const constraints = {video: true,};

navigator.mediaDevices.getUserMedia(constraints)
    .then((stream) => {
        player.srcObject = stream;
    });

setInterval(drawevery, 350);

function drawevery(){

    $(document).ready(function() {
        var image = canvas.toDataURL("image/png");
        $.post("server.php", { pimg: image } );
    });

    context.drawImage(player, 0, 0, canvas.width, canvas.height);
}

PHP代码：

<?php
    define('UPLOAD_DIR', 'path/');
    $img = $_POST['pimg'];
    $img = str_replace('data:image/png;base64,', '', $img);
    $img = str_replace(' ', '+', $img);
    $data = base64_decode($img);
    $file = UPLOAD_DIR . uniqid() . '.png';
    $success = file_put_contents($file, $data);
?>

但这只会导致空白图片。问题可能是在保存之前画布没有完全加载吗？如果是这样，如何解决？

编辑：更好的实现是这样，但它仍然不起作用：

function drawevery(){


context.drawImage(player, 0, 0, canvas.width, canvas.height);


     var img = new Image();

     img.onload=function(){       

     var image = canvas.toDataURL("image/png");

     $.post("savePic.php", { pimg: image } );

     }

img.src=canvas.toDataURL();

setTimeout(drawevery, 400);

}

标签： javascriptphpcanvashtml5-videocapture