如何使用canvas drawimage函数按照纵横比裁剪图像中心

var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');

var image = new Image();
image.src = 'image.jpg'; // 替换为你要裁剪的图像路径

image.onload = function() {
  var aspectRatio = image.width / image.height; // 计算纵横比
  var targetWidth = canvas.width;
  var targetHeight = canvas.height;
  
  if (aspectRatio > 1) {
    targetHeight = canvas.width / aspectRatio;
  } else {
    targetWidth = canvas.height * aspectRatio;
  }
  
  var offsetX = (canvas.width - targetWidth) / 2;
  var offsetY = (canvas.height - targetHeight) / 2;
  
  // 在canvas上绘制裁剪后的图像
  ctx.drawImage(image, offsetX, offsetY, targetWidth, targetHeight);
};

var croppedImage = new Image();
croppedImage.src = canvas.toDataURL(); // 获取裁剪后的图像数据URL