islacker

在发布文章中，如果文章中引用了远程图片，那么之前的做法就是：下载这个远程图片，然后重新上传。 
有了这个插件，你就可以省掉这些工作了，插件会在提交的时候，检查文章中引用的图片，如果是远程图片，就自动下载到附件目录，并保存到媒体库。 
如果没有选择特色图片，会自动选择第一张下载的图片作为特色图片。

Sync Remote Images

这个一个能在发布文章时同步文章中的远程图片的插件。

Fernan Díez

WordPress plugin for downloading automatically first remote image from a post and setting it as a featured image (when the post is saved as a draft or updated).
The purpose of this plugin is very simple: when a post is saved as a draft (not published) or updated (once published), it will fetch the first remote or external image that is referenced. The image that is retrieved is then attached to the post as the featured image. There are no additional settings to configure.
Usage
Avoid losing time in the process of setting featured image for each of your blog posts or page whenever you create new content from your WordPress blog site dashboard. This post retrieves the first remote or external image of your post and uses it as a featured image.
If you maintain multiple blogs, just copy paste the post contents from one blog to the other and this plugin will automatically save the first external image to the second blog. There is no need to re-upload images to multiple sites.
This plugin can also retrieve and save images from sites like Flickr, Facebook, Picasa, or any other image stock site once you have added it in your post editor just saving that single post. Remember that hotlinking is not a good practise.
No longer overwriting a post existing featured image function added.
Credits
<ul>
<li>Based on <a href="https://wordpress.org/plugins/auto-save-remote-images/">Auto Save Remote Image Plugin</a> created by Prebhdev Singh</li>
<li>New function added from <a href="https://github.com/cristoslc/wp-auto-save-remote-image" rel="nofollow ugc">WP Auto Save Remote Image Plugin</a> created by Cristos L-C.</li>
</ul>
Please do not use this plugin to violate copyrights. Don’t be evil.

Auto Save Remote Images (Drafts)

WordPress plugin for downloading automatically first remote image from a post and setting it as a featured image (when is saved as a draft or updated)

Sync Remote Images vs Auto Save Remote Images (Drafts)