Post thumbnails feature was introduced in WordPress 2.9. It allows you to add thumbnail images to posts, pages and custom post types. While Thesis theme offers a similar feature called Post Image and Thumbnail to work with post images, they are not quite the same thing. And plugins etc. which depend on post images may not work well with Thesis in lack of post images..
To enable this feature in Thesis WordPress Theme, you need to add the following lines of code in custom_functions.php:
add_theme_support( 'post-thumbnails' ); set_post_thumbnail_size( 500, 400); add_image_size( 'teaser', 240, 160, true );
The lines of code does three things.
- The first line, add_theme_support(‘post-thumbnails’), declares the support for post images. It requests the WordPress to feature the featured image box to the post / page editor.
- The next line defines the default post thumbnail size. You can change the width and height to your requirement.
- The last line specifies the additional sizes of the image to be used elsewhere; in teasers, featured posts and so on.
You can also style the thumbnails with CSS the way you want. Check out WordPress Codex to learn more about Post Thumbnails.