Wordpress: Get post thumbnail URLs as data attributes

post_thumbnail_data_attributes

// use inside the loop
// <div <?php post_class() ?> <?php post_thumbnail_data_attributes(); ?>>
// data-thumbnail-large="http://url.com/wp-content/uploads/2013/07/chicago-1000x703.jpg"
// data-thumbnail-medium="http://url.com/wp-content/uploads/2013/07/chicago-500x351.jpg"

function post_thumbnail_data_attributes() {

  $thumbnail_id     = get_post_thumbnail_id();

  $thumbnail_large  = wp_get_attachment_image_src($thumbnail_id, 'large');
  $data_attributes  = ' data-thumbnail-large="' . $thumbnail_large[0] .'" ';

  $thumbnail_medium = wp_get_attachment_image_src($thumbnail_id, 'medium');
  $data_attributes  .= ' data-thumbnail-medium="' . $thumbnail_medium[0] .'" ';

  echo $data_attributes;
}