如何在fabric js中获取背景图像属性

var canvas = new fabric.Canvas('canvas');

fabric.Image.fromURL('background.jpg', function(img) {
  canvas.setBackgroundImage(img, canvas.renderAll.bind(canvas));
}, { crossOrigin: 'anonymous' });

var backgroundImage = canvas.backgroundImage;
console.log(backgroundImage.width); // 获取背景图像的宽度
console.log(backgroundImage.height); // 获取背景图像的高度
console.log(backgroundImage.scaleX); // 获取背景图像的水平缩放比例
console.log(backgroundImage.scaleY); // 获取背景图像的垂直缩放比例

console.log(backgroundImage.left); // 获取背景图像的左侧位置
console.log(backgroundImage.top); // 获取背景图像的顶部位置
console.log(backgroundImage.angle); // 获取背景图像的旋转角度