获取图片的真实宽高

export function getImageSize(url: string): Promise<string> {
	return new Promise(function (resolve, reject) {
		let image = new Image();
		image.onload = function () {
			resolve(`${image.width}*${image.height}`);
		};
		image.onerror = function () {
			reject(new Error("error"));
		};
		image.src = url;
	});
}