Generate EAN13 barcode The project that I'm working on requires that I generate an EAN13 barcode for display on vouchers. 

I'm attempting to implement the following as a Craft Plugin: https://github.com/rlt3/php-barcode

The part that I am unclear about is how exactly to define my Model to return an image to the calling template. Do I even need a Model ?
Bit of a late reply (But hope you can use this!), but I created a plugin to output barcodes within Craft templates via Twig:

https://github.com/madebyshape/barcode

I created it because one of our clients required a barcode to be output in to a generated PDF that got sent to their customers.