This plugin enable bloggers to upload images, crop and save it as post thumbnails without manually copy-n-paste custom field values. For theme develop
wp-post-thumbnailfolder into your 'wp-content/plugins' folder.
Note: The default thumbnail is 160px by 90px which floats to the top left corner of the content of your post.
If your WordPress blog uses a theme that comes with pre-configured set of thumbnail(s) to work with this plugin, the theme's folder should contain an XML file called 'wppt.xml' created by the theme developer. In this case, it will override the default thumbnail.
For theme developers, more information on how to configure WP Post Thumbnail for your WordPress theme can be found in FAQ.