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:
<ul>
<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.

Alex Mills

By default, WordPress uses the center of an image when creating cropped thumbnails. SmartCrop attempts to find and use the most interesting part of an image and centers the cropping on that portion of the image.
This process is entirely automatic and cannot be manually controlled. There are other plugins out there if you wish to manually specify where you want thumbnails to be cropped.
Since this analysis process can be slow on large images, thumbnails are initially center cropped and later asynchronously regenerated to be smartly cropped. This avoids the uploading of new images from being slow. The one side effect of this however is that your browser may load and cache the centered thumbnail before it’s re-cropped.
Want to smartly crop your past image uploads? You can use my <a href="https://wordpress.org/plugins/regenerate-thumbnails/" rel="ugc">Regenerate Thumbnails</a> plugin to trigger that. Make sure to uncheck skipping existing thumbnails.
<h4>Need Help? Found A Bug? Want To Contribute Code?</h4>
Support for this plugin is provided via the <a href="https://wordpress.org/support/plugin/smartcrop" rel="ugc">WordPress.org forums</a>.
The source code for this plugin is available on <a href="https://github.com/Viper007Bond/smartcrop" rel="nofollow ugc">GitHub</a>.

SmartCrop

Instead of cropping to the center of an image, SmartCrop attempts to use the most interesting part of the image for the thumbnail.

Generate Post Thumbnails vs SmartCrop