Can anyone help with this AutoOpenGraph code that seems to appear in a few add ons? It appears to be the main part of the AutoFacebook OG add on, but while searching for help, I've found it referenced elsewhere, as well.

I'd like a simple way to get OpenGraph working on my site. This code might just work, except that, well, the main reason I'd like to install it is to get the appropriate product image to show up when someone decides to share a product URL to Facebook.

FB's Open Graph Object Debugger scrapes the product info well enough, but, unfortunately my main product image is too small for it. It wants a minimum 200px x 200px.

So, the AutoOpenGraph code that does this appears to be:
//get defined image or default
$myImage= zen_get_products_image((int)$_GET['products_id']);
$img = simplexml_load_string($myImage);
$img = $img['src'];

It looks to me like it's pulling the main image. Is there code that can be swapped in so that it would return the product image from the "large" images subdirectory? That might solve my problem.

Thanks!