Studiofreya

SF Generate Tags is a plugin that helps generate tags for posts. It scans the names of all attached images and/or the post content (text) and places the resulting tags in the built-in WordPress “Tags Widget” in the post editor. 
The plugin analyzes collected words and picks out the most suitable for tags. 
All tags are then sorted in descending order and posted into the Tags widget. 
If you don’t like a tag which has been discovered and want to delete them, you can just click the X button and save post without them. 
The plugin doesn’t mess with your existing tags. It preserves all your existing tags for the post. All the actions can be easily undone.
This plugin should work with any language. It’s filtering algorithm is designed for English. All other languages will have all the words be added as tags.
<a href="https://studiofreya.com/wordpress/sf-generate-tags/" rel="nofollow ugc">SF Generate Tags website</a>
<h4>Features:</h4>
<ul>
<li>Easy to use from the admin panel for post edit </li>
<li>Choose to generate tags from attached images or post text or both</li>
<li>Exclude words that you don’t want to be tags</li>
<li>Easy to remove all undesirable tags</li>
<li>All actions can be undone</li>
<li>Existing tags are preserved</li>
<li>Add other tags later</li>
<li>Regenerate tags after updating the post (or not)</li>
<li>Limit number of generated tags</li>
</ul>

SF Generate Tags

Generate tags for posts from images or/and post text.

DesignSmoke

<h3>Advanced Spintax Post Generator – Spintax Plugin for WordPress</h3>
Advanced Spintax Post Generator allows you to quickly create posts using your spintax templates.
Create multiple locations, events, posts and pages without duplicate content penalties using this free WordPress spintax plugin. For example, if you have multiple stores that all offer the same products, you can quickly create unique pages for each one.
This is a completely free (GPLv2) plugin created by <a href="https://www.designsmoke.com/" rel="nofollow ugc">DesignSmoke – Portland Web Development</a>
Features
<ul>
<li>Avoid Duplicate Content Penalties</li>
<li>Spin titles, descriptions, slugs, tags and categories</li>
<li>Supports all custom post types</li>
<li>
Create as many posts as you want
</li>
<li>
(Future release) Create templates for easy re-use
</li>
<li>(Future release) Featured images</li>
<li>(Future release) Create posts for each keyword in a list (EG: Store San Diego, Store Dallas, Store New York City)</li>
</ul>
FAQ
<ul>
<li>Can I modify this plugin?</li>
<li>Yes! The plugin is <a href="http://www.gnu.org/licenses/gpl-2.0.html" rel="nofollow ugc">licensed under the GPLv2 License</a>.</li>
</ul>

Advanced Spintax Post Generator

Advanced Spintax Post Generator - Spintax Plugin for WordPress

SF Generate Tags vs Advanced Spintax Post Generator