CakePHP: image inside link, want to make link point to image location

I have some images inside links that I want to essentially look like this:


Clicking on the link should load the image it contains. I'm trying to use CakePHP's HTML helper to do this, as follows:

<?php
  echo $html->link(
    $html->image('img.png'),
    'img.png',
    array('escape' => false)
  );
?>

When I do this, however, I get the following code:


Without using absolute URLs, can I make the link's href attribute point to the image's correct location?

Thanks!