marynixie

This plugin generates Featured Image for all posts at once.
It is based on WordPres 2.9+ feature – Post Thumbnails. This plugin takes the first image (by default) from post body and assignes it as a post Featured Image. It helps if your theme supports post thumbnails feature and you want to assign Featured Image for all your existing posts.
Plugin performs mass manipulation on posts Featured Image property and uploads files if they are stored externally. Don’t forget to backup your files and database before using this plugin.
It displays log of success/fails. There is also a feature to remove all Featured Images from all posts – this only changes post setting, no actual files are removed.
Related Links:
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<li><a href="http://wordpress.shaldybina.com/plugins/generate-post-thumbnails/" title="Generate Post Thumbnails Plugin for WordPress" rel="nofollow ugc">Plugin Homepage</a></li>
</ul>

Generate Post Thumbnails

Tool for mass generation of Wordpress posts thumbnails using the post images.

fahrirusliyadi

WordPress generates thumbnails in the same directory with the original image. This plugin change this behavior by generating the thumbnails in a separate directory. The thumbnails will only be generated when they are needed and has not been generated.
This plugin will only move the thumbnails location for new uploaded images. To move all thumbnails, you need to delete all existing thumbnails (see FAQ).

Fr Thumbnails Folder

Move thumbnails file location to {$upload_path}/thumbnails or {$upload_path}/sites/{$blog_id}/thumbnails for multisite.

Generate Post Thumbnails vs Fr Thumbnails Folder