How do I get a barcode in Magento email template

I found this out while scouring the net on my quest for all my other recent problems.

Zend has a built in barcode generation class, Zend_Barcode. Then googling php image output, I put together this little script I uploaded to var/export/_barcode.php:

<?php
require_once '../../app/Mage.php';
umask(0);
Mage::app();
Mage::app()->loadArea(Mage_Core_Model_App_Area::AREA_FRONTEND);
if( isset($_GET['ord']) && strlen($_GET['ord']) > 5 ) {
    header('Content-Type: image/jpeg');
    $barcodeOptions = array('text' => $_GET['ord']); 
    $rendererOptions = array(); 
    // Draw the barcode in a new image, 
    $imageResource = Zend_Barcode::draw( 
        'code39', 'image', $barcodeOptions, $rendererOptions 
    ); 
    imagejpeg($imageResource);

} else { echo "<pre><b>Error:</b> required input not found\n"; }
?>

If you visit this script’s URL with the standard GET, you’ll be served a scannable barcode. So put this in your Transactional Email template:

<img src="http://yourmagentowebsite.com/var/export/_barcode.php?ord={{var order.increment_id}}" 
    alt="{{var order.increment_id}}" 
    style="margin-bottom:10px;" 
    border="0"/>