Konrád Koller

This plugin helps you to fix any missing thumbnail issue in a fairly short time. The only thing you need to do is just few simple click and the plugin does the rest. It can be really helpful if you have thousands of images in your database.
You can regenerate thumbnails for each single image in your database or you can simply select those you really want to update. If you choose a post or page the plugin will regenerate thumbnails for each related images. You can choose from the following methods:
<ul>
<li>Regenerate thumbnails for all images in the database.</li>
<li>Bulk action in post liste: You can choose which one to update by checking the checkboxes.</li>
<li>Media library items: Move your mouse over the chosen image(s) and click on “Regenerate thumbnails” link.</li>
<li>Post editor: click on “Regenerate thumbnails” button which is next to “Add media” button. (Off by default)</li>
</ul>
Furthermore you can add your own thumbnails sizes, change default JPG compression rate and mass regenerate thumbnails. The best thing about this plugin is that you can use it with custom post types as well.

ONet Regenerate Thumbnails

Doesnt have 4.4.1 bulk generation support. But you can generate thumbnails one by one.



Doesnt have 4.4.1 support completely

Fix missing thumbnails in no time with few easy clicks. The plugin does the hard work.

Subrata Sarkar

Custom Thumbnail Generator is a powerful tool for defining and managing custom image sizes in WordPress.
Key Features
<pre><code>* **AJAX-powered Interface:** Add, remove, and regenerate thumbnails instantly without a page reload. 

* **Theme Independence:** Custom image sizes are decoupled from themes, ensuring they remain accessible and functional even when themes are switched. 

* **Consistent Image Handling:** Provides developers, photographers, and content creators with precise control over image dimensions.
</code></pre>
<h3>License</h3>
This plugin is licensed under the <a href="https://www.gnu.org/licenses/gpl-2.0.html" rel="nofollow ugc">GNU General Public License v2 or later (GPLv2+)</a>.
You are free to use, modify, and distribute this plugin under the terms of the GPL license.

Custom Thumbnail Generator

Custom Thumbnail Generator manages image sizes via an AJAX interface. It decouples sizes from themes, ensuring they persist and remain functional.

ONet Regenerate Thumbnails vs Custom Thumbnail Generator