puggan

You just uploaded a few images to you blog, and notice that the thumbnails cut off the heads of them, 
here is a tool to specify exactly how you want your thumbnails cut, you can zoom in and drag the thumnail 
area to the position that you want. 
This tool is even more useful in combination with theams and plugins that use of thumbnails.

Reposition Thumnails

A pluggin for the moments when the center of the picture wasn't that good as thumnail, so you can avoid cut of heads in yout thumbnails.

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.

Reposition Thumnails vs Force Regenerate Thumbnails