Cory Borrow has posted a tutorial he's created to show how to harness the power of PHP and GD to create thumbnail images out of the contents of a text file.

Today, I'll give a little info on how to achieve the process of creating a thumbnail using PHP, GD and the text from a text file. It is really pretty simple, so lets get started.

The trick behind the translation is in reading in the contents of the (plain) text file and pushing it into a string value of a newly created GD-generated image. He includes the code to make using it in your own app simple (a cut and paste version) - his method FileToThumb.