Perl Graphics Programming

Adding to Existing PDF Files

Each PDF::API2 object represents a top-level PDF document. The document can be created from scratch by adding pages and drawing on them by adding Gfx or Text objects, or it can be read from an existing PDF file. To manipulate an existing file, use the open( ) method when creating the top-level PDF object.

Example 12-4 opens an existing PDF file (with the name provided when the script is invoked) and adds a rotated “Confidential” stamp to each page. Once the document is successfully opened, a new font resource is added first, in case the existing document does not use the Helvetica font. Then, each page is accessed in turn by calling the openpage( ) method, which returns a reference to the Page object for a particular existing page. Next, the stamp is added to the page with a Text object. The text is moved into place and rotated using the transform( ) method, as more than one transformation is being performed on the same object. The result is written back to the original document with the update( ) method.

Example 12-4. Modifying an existing PDF file

#!/usr/bin/perl -w # # Example 12-4. Add a stamp to an existing document. use strict; use PDF::API2; # Used to generate the PDF output unless (defined($ARGV[0])) { die "Please provide a filename.\n"; } # Open the PDF file whose name was provided on the command line my $pdf = PDF::API2->open($ARGV[0]) or die "Couldn't open $ARGV[0]!\n"; # Initialize the font used to create the stamp my $font = $pdf->corefont('Helvetica'); ...