D7: file_create_url() usable in node.tpl.php? Can you use file_create_url() inside node.tpl.php? Should I assume you can only use it in the template.php?

$img_src = render($content['field_image']);
$bgimage = file_create_url($img_src);


Using the following code, I am only getting public://science-of-rock_background.png from $img_src.
Is there any reason why it would be blank?

print $img_src;
print $bgimage;




Edit made to avoid confusion: 

In my tpl page for this field I am generating the uri.

field--field_image.tpl.php 

&lt;?php foreach ($items as $delta =&gt; $item) : ?&gt;
  &lt;?php 
  print $item['#item']['uri']; 
  ?&gt;
&lt;?php endforeach; ?&gt;
file_create_url takes a uri, such as public://science-of-rock_background.png

The revised:

$img_src = $content['field_image'];
$bgimage = file_create_url($img_src);

Would work if your field is only returning the URI.

And, for best practices, should set that up in preprocess_node, otherwise will work in node.tpl.php