WP Overnight - Barcode in Invoice

functions.php

<?php
function redlight_overnight_barcode_scanner_wc_barcode( $template_type, $order ) {
	if(function_exists('WC_Order_Barcodes')){
		echo '<style type="text/css">.barcode>img{max-width:100%;max-height:100%;}</style>';
		echo '<div class="barcode" style="width:250px;text-align: center;">';
		echo WC_Order_Barcodes()->display_barcode($order->get_id(),$order->get_order_number(),'',true);
		echo '</div>';
	}

}
add_action( 'wpo_wcpdf_after_document_label', 'redlight_overnight_barcode_scanner_wc_barcode', 10, 2 );