Add intro for img_path

_posts/2019-08-08-write-a-new-post.md

@@ -206,6 +206,31 @@ The parsing result will automatically add the CDN prefix `https://cdn.com` befor
 ```
 {: .nolineno}
 
+### Image path
+
+When a post contains many images, it will be a time-consuming task to repeatedly define the path of the images. To solve this, we can define this path in the YAML block of the post:
+
+```yml
+---
+img_path: /img/path/
+---
+```
+{: .nolineno }
+
+And then, the image source of Markdown can write the file name directly:
+
+```md
+![The flower](flower.png)
+```
+{: .nolineno }
+
+The output will be:
+
+```html
+<img src="/img/path/flower.png" alt="The flower">
+```
+{: .nolineno }
+
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