For the encoding there is basically only one modification available.

For those symbologies that include an optional checksum it is possible to enable or disable this calculation.

The following symbologies may have optional checksum character(s)

Turning on/off checksum calculation for other symbologies will have no affect. Checksum calculation is enabled with a call to AddChecksum() on the chosen backend.

For example to augment the previous "CODE 39" example to include the checksum the code would be changed to

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<?php
$symbology = BarcodeFactory::Create (ENCODING_CODE39 );
$symbology->AddChecksum();
$barcode = BackendFactory ::Create('IMAGE', $symbology);
$barcode->Stroke('ABC123');
?>

Which would give the result shown in Figure 24.6

Figure 24.6. Encoding "ABC123" with CODE 39 adding checksum (checksum=4).

The output format can be adjusted by specifying/creating the appropriate backend. The library supports image and postscript (and encapsulated postscript) backends.

The backend is created by calling the static factory method

So to create an image backend the following code is needed

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$barcode = BackendFactory::Create (BACKEND_IMAGE ,$symbology);

Where "$symbology" is the chosen symbology as created by the BarcodeFactory::Create() factory method. Please note that both factory functions are called as static methods.

The output format is specified by using one of the following symbolic defines

To send the created stream (either image or postscript) back to the browser or to a file the Backend::Stroke() method shall be used. The parameter to the Stroke() method shall be the string to be encoded.

Assume we want to create an image that is sent back to the browser. We would then use the following code

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<?php
$symbology = BarcodeFactory::Create (ENCODING_CODE128 );
$barcode = BackendFactory ::Create(BACKEND_IMAGE, $symbology);
$barcode->Stroke('ABC123');
?>

It is also possible to write the barcode directly to a file by specifying a second argument to the Stroke() method above. So if we instead wanted the barcode to be stored in the file "/tmp/barcode.png" we could write

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$symbology = BarcodeFactory::Create (ENCODING_CODE128 );
$barcode = BackendFactory ::Create(BACKEND_IMAGE, $symbology);
$barcode->Stroke('ABC123','/tmp/barcode.png');

Again, please note that for the Postscript background the Backend::Stroke() method normally returns the postscript file as a string if everything went well.

This is done by adding a second argument, the file name, to the Backend::Stroke() method. This works for all backends. The file name should be an absolute path name. Since it is the PHP process that writes the file the permissions must allow the PHP process to write to the directory if PHP is called from a browser. If the command line version of PHP is used this does of course not apply.

The human readable text is the string that can optionally be displayed at the bottom of the bar. By default this is enabled.

There are however some subtle facts regarding the module width and backend that needs to be explained.

This also means that for image type backends only integer values makes sense.

The following code shows how to both change the module width to 2 pixels and hide the human readable text

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<?php
$symbology = BarcodeFactory::Create (ENCODING_CODE39 );
$barcode = BackendFactory ::Create('IMAGE', $symbology);
$barcode ->SetModuleWidth (2);
$barcode ->HideText();
$barcode ->Stroke('ABC123');
?>

which would give the result shown in Figure 24.7 below

Figure 24.7. Encoding "ABC123" with CODE 39, hiding the text.

Will rotate the barcode 90 degrees to create a vertical view of the barcode.

The height of the bar codes is specified with the Backend::SetHeight() method. For images the height is interpreted as pixels and for postscript files it is interpreted as points (1 pt = 1/72 inch)

The scale factor is real number and specifies a scale factor for the overall barcode image.

This method will enable a frame around the edges of the barcode image

The following example outputs a postscript file representing the bar code with a module width of 1.2 pt, using a vertical layout and scaling the image 2 times. For this example we are using CODE 39 with a checksum (which is automatically generated)

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<?php
$symbology = BarcodeFactory::Create (ENCODING_CODE128 );
$barcode = BackendFactory ::Create(BACKEND_PS, $symbology);
$barcode->SetVertical(true);
$barcode->Scale(2);
$barcode->SetModuleWidth(1.2);
$barcode ->Stroke('ABC123') ) {
?>