PHP Function to grab the Featured Image (Wordpress) and Integrate in Pinterest Button

PHP Function to grab the Featured Image (Wordpress) and Integrate in
Pinterest Button

I have this code inserted in the Function.PHP file of my wordpress this.
What it basically do is
If the user click on the Pinterest PIN IT Button, It checks the blog post
page for the FIRST Image and return it to be Pinned in Pinterest.
Is it possible if someone can modify the code so that it will totally
ignore all the images in the blog post page and instead choose the
Featured Image?
Catch the First image funtion:
function catch_that_image() {
global $post, $posts;
$first_img = '';
ob_start();
ob_end_clean();
$output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i',
$post->post_content, $matches);
$first_img = $matches [1] [0];
if(empty($first_img)){ //Defines a default image
$first_img =
"http://www.bendaggers.com/wp-content/themes/Lord%20of%20Avernus%20-%20Abaddon/Images/Deafult_Img.png";
}
return $first_img;
}
Wordpress Featured Image:
<?php the_post_thumbnail(); ?>