Update the tutorial on comments and image attributes

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

@@ -32,16 +32,19 @@ tags: [TAG]     # TAG names should always be lowercase
 
 ### Timezone of Date
 
-In order to accurately record the release date of a post, you should not only set up the `timezone` of `_config.yml` but also provide the post's timezone in variable `date` of its Front Matter block. Format: `+/-TTTT`, e.g. `+0800`.
+In order to accurately record the release date of a post, you should not only set up the `timezone` of _\_config.yml_ but also provide the post's timezone in variable `date` of its Front Matter block. Format: `+/-TTTT`, e.g. `+0800`.
 
 ### Categories and Tags
 
 The `categories` of each post are designed to contain up to two elements, and the number of elements in `tags` can be zero to infinity. For instance:
 
 ```yaml
+---
 categories: [Animal, Insect]
 tags: [bee]
+---
 ```
+
 ### Author Information
 
 The author information of the post usually does not need to be filled in the _Front Matter_ , they will be obtained from variables `social.name` and the first entry of `social.links` of the configuration file by default. But you can also override it as follows:
@@ -56,7 +59,7 @@ author:
 
 ## Table of Contents
 
-By default, the **T**able **o**f **C**ontents (TOC) is displayed on the right panel of the post. If you want to turn it off globally, go to `_config.yml` and set the value of variable `toc` to `false`. If you want to turn off TOC for a specific post, add the following to the post's [Front Matter](https://jekyllrb.com/docs/front-matter/):
+By default, the **T**able **o**f **C**ontents (TOC) is displayed on the right panel of the post. If you want to turn it off globally, go to _\_config.yml_ and set the value of variable `toc` to `false`. If you want to turn off TOC for a specific post, add the following to the post's [Front Matter](https://jekyllrb.com/docs/front-matter/):
 
 ```yaml
 ---
@@ -66,7 +69,9 @@ toc: false
 
 ## Comments
 
-Similar to TOC, the [Disqus](https://disqus.com/) comments are loaded by default in each post, and the global switch is defined by variable `comments` in file `_config.yml` . If you want to close the comment for a specific post, add the following to the **Front Matter** of the post:
+The global switch of comments is defined by variable `comments.active` in the file _\_config.yml_. After selecting a comment system for this variable, comments will be turned on for all posts.
+
+If you want to close the comment for a specific post, add the following to the **Front Matter** of the post:
 
 ```yaml
 ---
@@ -98,26 +103,7 @@ Then you can use it like other markdown languages: surround the graph code with
 
 ## Images
 
-### Preview image
-
-If you want to add an image to the top of the post contents, specify the attribute `src`, `width`, `height`, and `alt` for the image:
-
-```yaml
----
-image:
-  src: /path/to/image/file
-  width: 1000   # in pixels
-  height: 400   # in pixels
-  alt: image alternative text
----
-```
-
-Except for `alt`, all other options are necessary, especially the `width` and `height`, which are related to user experience and web page loading performance. Later section ["Image size"](#image-size) will also mention this.
-
-Starting from _Chirpy v5.0.0_, the attributes `height` and `width` support abbreviations: `height` → `h`, `width` → `w`.
-
-
-### Image caption
+### Caption
 
 Add italics to the next line of an image，then it will become the caption and appear at the bottom of the image:
 
@@ -127,7 +113,7 @@ _Image Caption_
 ```
 {: .nolineno}
 
-### Image size
+### Size
 
 In order to prevent the page content layout from shifting when the image is loaded, we should set the width and height for each image:
 
@@ -143,7 +129,7 @@ Starting from _Chirpy v5.0.0_, `height` and `width` support abbreviations (`heig
 ```
 {: .nolineno}
 
-### Image position
+### Position
 
 By default, the image is centered, but you can specify the position by using one of the classes `normal`, `left`, and `right`. For example:
 
@@ -172,7 +158,7 @@ By default, the image is centered, but you can specify the position by using one
 
 > **Limitation**: Once the position of the image is specified, the image caption should not be added.
 
-### Image shadow
+### Shadow
 
 The screenshots of the program window can be considered to show the shadow effect, and the shadow will be visible in the `light` mode:
 
@@ -183,7 +169,7 @@ The screenshots of the program window can be considered to show the shadow effec
 
 ### CDN URL
 
-If you host the images on the CDN, you can save the time of repeatedly writing the CDN URL by assigning the variable `img_cdn` of `_config.yml` file:
+If you host the images on the CDN, you can save the time of repeatedly writing the CDN URL by assigning the variable `img_cdn` of _\_config.yml_ file:
 
 ```yaml
 img_cdn: https://cdn.com
@@ -206,7 +192,7 @@ The parsing result will automatically add the CDN prefix `https://cdn.com` befor
 ```
 {: .nolineno}
 
-### Image path
+### 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:
 
@@ -231,6 +217,25 @@ The output will be:
 ```
 {: .nolineno }
 
+
+### Preview Image
+
+If you want to add an image to the top of the post contents, specify the attribute `src`, `width`, `height`, and `alt` for the image:
+
+```yaml
+---
+image:
+  src: /path/to/image/file
+  width: 1000   # in pixels
+  height: 400   # in pixels
+  alt: image alternative text
+---
+```
+
+Except for `alt`, all other options are necessary, especially the `width` and `height`, which are related to user experience and web page loading performance. The above section "[Size](#size)" also mentions this.
+
+Starting from _Chirpy v5.0.0_, the attributes `height` and `width` can be abbreviated: `height` → `h`, `width` → `w`. In addition, the [`img_path`](#image-path) can also be passed to the preview image, that is, when it has been set, the  attribute `src` only needs the image file name.
+
 ## Pinned Posts
 
 You can pin one or more posts to the top of the home page, and the fixed posts are sorted in reverse order according to their release date. Enable by: