如题，在将页面的图片地址进行本地输出时（Html2Canvas.js），因不同源存在跨域问题，会出现toDataURL访问权限问题：
【Redirect at origin ‘http://sub1.xx.com’ has been blocked from loading by Cross-Origin Resource Sharing policy: No ‘Access-Control-Allow-Origin’ header is present on the requested res
