如何在画布上的图层中绘制图像？

<canvas id="myCanvas" width="500" height="500"></canvas>

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

context.fillStyle = "red";
context.fillRect(x, y, width, height);

context.fillStyle = "blue";
context.beginPath();
context.arc(x, y, radius, startAngle, endAngle);
context.closePath();
context.fill();

context.font = "20px Arial";
context.fillStyle = "black";
context.fillText("Hello World", x, y);

var img = new Image();
img.src = "image.jpg";
img.onload = function() {
  context.drawImage(img, x, y, width, height);
};

context.globalAlpha = 0.5;

context.globalCompositeOperation = "lighter";

context.translate(x, y);
context.scale(scaleX, scaleY);
context.rotate(angle);

context.clearRect(x, y, width, height);