jewpi

Generates properly formatted post thumbnails on-the-fly for plugins and themes. 
Fallback thumbnails, remote images, Youtube videos supported.
<h4>Donations</h4>
If you like and use ThumbMaster you could <a href="https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=UV2FDM29SNY6W" rel="nofollow ugc">consider some donation</a> to the author.

ThumbMaster

Generates properly formatted post thumbnails on-the-fly for plugins and themes.

nosilver4u

Pedro Elsner

Force Regenerate Thumbnails allows you to delete all old images sizes and REALLY regenerate the thumbnails for your uploads.
Regenerate all thumbnails from the Tools admin menu. Regenerate batches of images via the Media Library list mode. Select the images to regenerate and then use the Bulk Actions drop-down menu to Force Regenerate Thumbnails. Use attachment actions to regenerate thumbnails for a single image.
Several filters exist for advanced usage. See more via <a href="https://gist.github.com/nosilver4u/eb858df10521aece2044a3a15ccdd17b" rel="nofollow ugc">this gist</a>.
You may report security issues through our Patchstack Vulnerability Disclosure Program. The Patchstack team helps validate, triage and handle any security vulnerabilities. <a href="https://patchstack.com/database/vdp/force-regenerate-thumbnails" rel="nofollow ugc">Report a security vulnerability.</a>

Force Regenerate Thumbnails

Delete and REALLY force thumbnail regeneration.

ThumbMaster vs Force Regenerate Thumbnails