如何在使用画布绘制图像时保持内部div的阴影？

<div id="container">
  <canvas id="canvas"></canvas>
  <div id="innerDiv">这是内部div的内容</div>
</div>

#innerDiv {
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
}

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

var image = new Image();
image.src = "image.jpg";
image.onload = function() {
  ctx.drawImage(image, 0, 0);
}

#canvas {
  position: absolute;
  top: 0;
  left: 0;
  opacity: 0;
}