Targeting only post thumbnails for rebuild

Hey, awesome plugin. great job. very useful!

I had to run this on a site with a massive, massive, amount of images after a change to the template and re-structuring of post thumbnail sizes. We didn’t need to hit every single image for a rebuild so i modified your plugin to only hit images marked as a post thumbnail.

I think that this would be a great option to include, so i’m including the code i used. i’m sure there’s probably a better way to code that up, but this worked for me. i just swapped this code in around line 158 and replaced the existing $attachments.

//query only featured image id's
		$featured_images = $wpdb->get_results( "SELECT meta_value FROM {$wpdb->postmeta}
		                                        WHERE meta_key = '_thumbnail_id'" );

		//convert the featured_images array down into one dimensional array of id's
		$thumbs = array();
		foreach($featured_images as $image) {
			array_push($thumbs, $image->meta_value);
		}

		//re-recreate attachemtns to get_posts
		$attachments =& get_posts( array(
			'post_type' => 'attachment',
			'post_mime_type' => 'image',
			'post_status' => null,
			'numberposts' => 200,
			'offset'=> 0,
			'orderby' => 'post_date',
			'order' => 'DESC',
			'post__in' => $thumbs, // any parent
			'output' => 'object'
		) );