pdfa/transparent_stamp_for_pdfa

Apply a transparent stamp to an existing PDF/A document while maintaining PDF/A conformance.
Import all pages from an existing PDF/A document and place a stamp on the page. The stamp is filled with a pattern color, where the pattern consists of a bitmap. The bitmap is used as a mask to create a certain percentage of transparency. This is required since real transparency is not allowed in PDF/A. Transparency by pattern color is PDF/A compatible, so we use it to apply a transparent stamp on a PDF/A document while maintaining PDF/A conformance.
Note: On Windows systems the "Arial-Bold" font is installed by default. On other systems, you may have to load another font if the "Arial-Bold" font is not available.

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<?php

/* $Id: transparent_stamp_for_pdfa.php,v 1.7 2012/05/03 14:00:37 stm Exp $

* Transparent stamp for PDF/A:

* Apply a transparent stamp to an existing PDF/A document while maintaining

* PDF/A conformance.

* Import all pages from an existing PDF/A document and place a stamp on the

* page. The stamp is filled with a pattern color, where the pattern consists of

* a bitmap The bitmap is used as a mask to create a certain percentage of

* transparency. This is required since real transparency is not allowed in

* PDF/A. Transparency by pattern color is PDF/A compatible, so we use it to

* apply a transparent stamp on a PDF/A document while maintaining PDF/A

* conformance.

* Note: On Windows systems the "Arial-Bold" font is installed by default.

* On other systems, you may have to load another font if the "Arial-Bold" font

* is not available.

* Required software: PDFlib+PDI/PPS 7

* Required data: PDF document

/* This is where the data files are. Adjust as necessary. */

$searchpath = dirname(dirname(dirname(__FILE__)))."/input";

$outfile = "";

$title = "Transparent Stamp for PDF/A";

$pdffile = "PLOP-datasheet-PDFA-1b.pdf";

/* data set for our halftoning bitmap */

$data = array(array(

0x00, 0x00, /* 30% */

0x00, 0x00,

0x03, 0xC0,

0x07, 0xE0,

0x0F, 0xF0,

0x1F, 0xF8,

0x0F, 0xF0,

0x07, 0xE0,

0x03, 0xC0,

0x00, 0x00,

),array(

0x00, 0x00, /* 20% */

0x00, 0x00,

0x03, 0xC0,

0x07, 0xE0,

0x0F, 0xF0,

0x07, 0xE0,

0x03, 0xC0,

0x00, 0x00,

));

$ht = 1; /* index in halftone array */

try {

$p = new PDFlib();

$p->set_parameter("SearchPath", $searchpath);

/* This means we must check return values of load_font() etc. */

$p->set_parameter("errorpolicy", "return");

$p->set_parameter("textformat", "utf8");

if ($p->begin_document($outfile, "pdfa=PDF/A-1b:2005") == 0)

throw new Exception("Error: " . $p->get_errmsg());

$p->set_info("Creator", "PDFlib Cookbook");

$p->set_info("Title", $title);

/* -----------------------------------------------------------------

* Open the input PDF.

* This must be done before creating the pattern because the output

* intent must be set before defining the pattern.

* -----------------------------------------------------------------

$indoc = $p->open_pdi_document($pdffile, "");

if ($indoc == 0)

throw new Exception("Error: " . $p->get_errmsg());

$endpage = (int) $p->pcos_get_number($indoc, "length:pages");

/* Since the input document contains its own output intent retrieve

* the output intent from the input document and copy it to the output

* document.

$res = $p->pcos_get_string($indoc, "type:/Root/OutputIntents");

if ($res == "array") {

$ret = $p->process_pdi($indoc, -1, "action=copyoutputintent");

if ($ret == 0)

throw new Exception("Error: " . $p->get_errmsg());

}

/* -------------------------------------------------------------------

* Define a bitmap pattern based on an image mask.

* We scale down the image to provide a smoother appearance on screen.

* -------------------------------------------------------------------

$bitmap ="";

for ($j=0; $j < count($data[$ht]); $j++) {

$bitmap .= sprintf("%c",$data[$ht][$j]);

}

// $bitmap[$j] = $data[$ht][$j];

$p->create_pvf("/pvf/image/bitmap", $bitmap, "");

$image = $p->load_image("raw", "/pvf/image/bitmap",

"bpc=1 components=1 height=16 width=16 invert mask");

if ($image == 0)

throw new Exception("Error: " . $p->get_errmsg());

$w = 16/32;

$pattern = $p->begin_pattern($w, $w, $w, $w, 1);

$p->fit_image($image, 0, 0, "scale=" . 1/32);

$p->end_pattern();

$p->close_image($image);

/* Loop over all pages of the input document */

for ($pageno = 1; $pageno <= $endpage; $pageno++)

{

$page = $p->open_pdi_page($indoc, $pageno, "");

if ($page == 0)

throw new Exception("Error: " . $p->get_errmsg());

/* Dummy page size; will be adjusted later */

$p->begin_page_ext(10, 10, "");

/* Place the imported page on the output page, and adjust the page

* size.

$p->fit_pdi_page($page, 0, 0, "adjustpage");

* Load the font for the stamp.

$font = $p->load_font("DejaVuSerif", "unicode", "embedding");

if ($font == 0)

throw new Exception("Error: " . $p->get_errmsg());

/* Place the stamp, filled with the pattern color */

$p->setcolor("fill", "pattern", $pattern, 0, 0, 0);

$p->fit_textline("PUBLISHED", 20, 20,

"font=" . $font . " fontsize=1 boxsize={550 800} stamp=ll2ur");

$p->close_pdi_page($page);

$p->end_page_ext("");

}

$p->end_document("");

$buf = $p->get_buffer();

$len = strlen($buf);

header("Content-type: application/pdf");

header("Content-Length: $len");

header("Content-Disposition: inline; filename=transparent_stamp_for_pdfa.pdf");

print $buf;

} catch (PDFlibException $e){

die("PDFlib exception occurred:\n" .

"[" . $e->get_errnum() . "] " . $e->get_apiname() .

": " . $e->get_errmsg() . "\n");

} catch (Exception $e) {

die($e->getMessage());

}

$p=0;