How can I display an image within a node with an SRC value that incorporates a URL taken from another field? I'm creating a directory of useful (web based) resources for a community. I'd like to use Drupal 7, but can use Drupal 6 if absolutely necessary. I don't mind installing any additional useful modules.

I'd like to create a node with a link field that stores the URL of the useful resource.

I'd like to display a screenshot of this URL, using WordPress's mshots feature, as part of the node.

So, as an example, the value of the link field would be:


  http://mashable.com/guidebook/twitter/


Within my content type template, or as an image field, or however you suggest I do it, this URL would need to be encoded and inserted into an image SRC value to give:


  http://s.wordpress.com/mshots/v1/http%3A%2F%2Fmashable.com%2Fguidebook%2Ftwitter%2F?w=500


Which shows a 500px wide screenshot of that URL.

What do you think would be the best way of doing this? I could use 'rewrite the output of this field' in Views, but I'd like the screenshot to be shown in the node view too.
You could use a custom 'screenshot' formatter for the link field. Further info for D6 and D7.