WordPress.org

Usage

The typical WordPress way

• Put add_image_size( 'my_custom_thumbnail_name', 220, 130, true ); in your theme’s functions.php file.
• Add the code to display that attachment’s thumbnail where you want it to appear: echo wp_get_attachment_image($attachment_id, 'my_custom_thumbnail_name');
• Unlike WordPress by itself, Custom Image Sizes will generate the thumbnail for an image, even if the image was uploaded before this add_image_size() was set.

A more direct Custom Image Sizes way

• Call wp_get_attachment_image_src() or wp_get_attachment_image() with the desired thumbnail '[width]x[height]' dimensions, like so:

echo wp_get_attachment_image($attachment_id, '220x80');

      /**
       * The above prints markup like
       * <img width="220" height="80" title="" alt=""
       *    class="attachment-220x80" src="http://www.example.com/path-to-file/something-220x80.jpg" />
       */