WordPress Real Thumbnail Generator

Description

It is easy to create a custom structure and regenerate thumbnails in bulk or individually (resized images uploaded).
Real Thumbnail generator allows you to efficiently regenerate (existing thumbnails) in your media library. You can generate a single image, or images in mass. You can create your own custom thumbnail upload structure with the plugin.
Due to chunked generation, thumbnails can regenerate up to 33% quicker than other plugins. Install this plugin, and it will work with all of your media and image files. A useful feature is that you can detect and delete unused image sizes, such as if you changed your WordPress theme. This plugin also supports WordPress multisites.