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Transparency
InformationsAuthor: Martin Hall-May
License: Freeware
DescriptionThis script gives transparency support. You can set the alpha channel from 0 (fully
transparent) to 1 (fully opaque). It applies to all elements (text, drawings, images).
Note: transparency requires at least Acrobat Reader 5.
Source
<?php
require('fpdf.php');
class AlphaPDF extends FPDF
{
var $extgstates;
function AlphaPDF($orientation='P', $unit='mm', $format='A4')
{
parent::FPDF($orientation, $unit, $format);
$this->extgstates = array();
}
// alpha: real value from 0 (transparent) to 1 (opaque)
// bm: blend mode, one of the following:
// Normal, Multiply, Screen, Overlay, Darken, Lighten, ColorDodge, ColorBurn,
// HardLight, SoftLight, Difference, Exclusion, Hue, Saturation, Color, Luminosity
function SetAlpha($alpha, $bm='Normal')
{
// set alpha for stroking (CA) and non-stroking (ca) operations
$gs = $this->AddExtGState(array('ca'=>$alpha, 'CA'=>$alpha, 'BM'=>'/'.$bm));
$this->SetExtGState($gs);
}
function AddExtGState($parms)
{
$n = count($this->extgstates)+1;
$this->extgstates[$n]['parms'] = $parms;
return $n;
}
function SetExtGState($gs)
{
$this->_out(sprintf('/GS%d gs', $gs));
}
function _enddoc()
{
if(!empty($this->extgstates) && $this->PDFVersion<'1.4')
$this->PDFVersion='1.4';
parent::_enddoc();
}
function _putextgstates()
{
for ($i = 1; $i <= count($this->extgstates); $i++)
{
$this->_newobj();
$this->extgstates[$i]['n'] = $this->n;
$this->_out('<</Type /ExtGState');
foreach ($this->extgstates[$i]['parms'] as $k=>$v)
$this->_out('/'.$k.' '.$v);
$this->_out('>>');
$this->_out('endobj');
}
}
function _putresourcedict()
{
parent::_putresourcedict();
$this->_out('/ExtGState <<');
foreach($this->extgstates as $k=>$extgstate)
$this->_out('/GS'.$k.' '.$extgstate['n'].' 0 R');
$this->_out('>>');
}
function _putresources()
{
$this->_putextgstates();
parent::_putresources();
}
}
?>
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Example
<?php
require('alphapdf.php');
$pdf = new AlphaPDF();
$pdf->AddPage();
$pdf->SetLineWidth(1.5);
// draw opaque red square
$pdf->SetFillColor(255, 0, 0);
$pdf->Rect(10, 10, 40, 40, 'DF');
// set alpha to semi-transparency
$pdf->SetAlpha(0.5);
// draw green square
$pdf->SetFillColor(0, 255, 0);
$pdf->Rect(20, 20, 40, 40, 'DF');
// draw jpeg image
$pdf->Image('lena.jpg', 30, 30, 40);
// restore full opacity
$pdf->SetAlpha(1);
// print name
$pdf->SetFont('Arial', '', 12);
$pdf->Text(46, 68, 'Lena');
$pdf->Output();
?>
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View the result here.
DownloadZIP | TGZ
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