By choosing the appropriate backend you can choose to generate the barcode label as either an image (in either PNG or JPEG format) or as Postscript (both standalone and Encapsulated postscript) . For images the PNG is strongly recommended and used by default. The reason is that PNG is a non-destructive format and will ensure the maximum quality of the barcodes while JPEG is not well suited for this type of applications since it is a destructive format.

This choice is being made by creating the appropriate backend. The backend is created by calling the factory method PDF417BackendFactory::Create() specifying what type of backend and what encoder to use. The backend factory will then return a suitable encoder.

The following code snippet shows how to create a backend that will generate an image.

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<?php
// Create a new encode using the default error correction
// and columns
$encoder = new PDF417Barcode ();
$backend = PDF417BackendFactory::Create( BACKEND_IMAGE, $encoder);
?>

It is also possible to have one encoder and two different backends to allow the creation of both image and postscript output at the same time as the following example shows

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<?php
$date='ABC123';
$file=' ...'; // Some filename to write the PS file to
 
// Create a new encode using the default error correction
// and columns
$encoder = new PDF417Barcode ();
 
$eImg = PDF417BackendFactory::Create( BACKEND_IMAGE, $encoder);
$eEPS = PDF417BackendFactory::Create( BACKEND_EPS, $encoder);
$eEPS->Stroke($data,$file);
$eImg->Stroke($data);
?>

In the list below is a short description of the available possibilities to change the output. For a more detailed explanation of the parameters for each method please consult the method reference at the end of this chapter