add download image

README.md

@@ -4,6 +4,7 @@
 
 * [1.图片上传](#1)
 * [2.图片拼接](#2)
+* [4.图片下载](#3)
 
 ------
 ## 前置安装
@@ -216,6 +217,26 @@ location /image_append {
 └── image_append.lua
 ```
 
+<h2 id="3">3.图片下载</h2>
 
+- music-room配置
 
+```nginx configuration
+# 子域名配置文件路径
+# /usr/local/openresty/nginx/conf.d/music-room.conf
 
+# server contex 中添加location
+
+#Donwload image use ngx.exec
+location /download_image2 {
+    content_by_lua_file /usr/local/openresty/nginx/conf/lua/download_image2.lua;
+}
+```
+
+- 添加lua脚本
+
+```bash
+/usr/local/openresty/resty_funcs
+.
+└── download_image.lua
+```