如何在画布上调整居中图像的大小？

// 获取画布和图像对象
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var image = new Image();

// 图像加载完成后执行
image.onload = function() {
  // 获取画布和图像的尺寸
  var canvasWidth = canvas.width;
  var canvasHeight = canvas.height;
  var imageWidth = image.width;
  var imageHeight = image.height;

  // 计算调整后的尺寸
  var newWidth, newHeight;
  if (imageWidth > canvasWidth) {
    newWidth = canvasWidth;
    newHeight = (canvasWidth / imageWidth) * imageHeight;
  } else if (imageHeight > canvasHeight) {
    newWidth = (canvasHeight / imageHeight) * imageWidth;
    newHeight = canvasHeight;
  } else {
    newWidth = imageWidth;
    newHeight = imageHeight;
  }

  // 计算绘制起始坐标
  var x = (canvasWidth - newWidth) / 2;
  var y = (canvasHeight - newHeight) / 2;

  // 绘制调整后的图像
  ctx.drawImage(image, x, y, newWidth, newHeight);
};

// 加载图像
image.src = 'path/to/image.jpg';