perf: 优化大屏的背景渲染方式，提升性能

src/utils/utils.ts

@@ -100,6 +100,15 @@ export const isMac = () => {
   return /macintosh|mac os x/i.test(navigator.userAgent)
 }
 
+/** 
+ * * file转url
+*/
+export const fileToUrl = (file:File): string => {
+  const Url = URL || window.URL || window.webkitURL;
+  const ImageUrl = Url.createObjectURL(file);
+  return ImageUrl
+};
+
 /** 
  * * file转base64
 */