make readme image smaller

Author: evopen

README.md

@@ -22,7 +22,7 @@ download prebuilt binary from [releases].
 
 This is a GUI program, and has a commandline interface(incomplete, mainly focus on gui). 
 
-![Interface](images/interface.png)
+![Interface](images/interface.jpg)
 
 Here are some parameters on the right panel of the program.
 

README_zh.md

@@ -25,7 +25,7 @@
 
 程序有图形界面也有命令行接口（不完整）
 
-![Interface](images/interface.png)
+![Interface](images/interface.jpg)
 
 图形界面的右侧参数如下，