Dynamically creating barcodes

I recently wrote a neat png image barcode generator. This was used in my html representation of an invoice. (see: http://tiki-lounge.com/~lussie/invoices.html)

Type in your favorite string of characters below.

Anything you enter with non-numeric characters will return a Code39 Barcode.

If you enter seven digits, it will return an EAN-8 Barcode with the last number as a checksum character.

If you enter 12 digits, it will return an EAN-13 Barcode with the last number as a checksum character.

Anything else that you enter will return an ITF Barcode.