How do I get the size (file size in Kb or MB) of an featured image in post?

I need to display some featured image info on post page. One of those data I need to display is file size of image (featured image of post).

I tried this function inside single.php.

<?php
function getSize($file){
$bytes = filesize($file);
$s = array('b', 'Kb', 'Mb', 'Gb');
$e = floor(log($bytes)/log(1024));
return sprintf('%.2f '.$s[$e], ($bytes/pow(1024, floor($e))));}
?>

and than to echo that size with:

<?php
echo getSize('/wp-content/uploads/2014/06/image-file-name.jpg');
?>

And it works fine, but what I need is help to make ti automatically grab featured image url, not to manually enter it?

For example I use this to echo featured image (“full”) url:

<?php
 if ( has_post_thumbnail()) {
   $full_image_url = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), 'full');
echo $thumb_image_url[0];
 }
?>

Any help to combine it?