Transparency
This demo shows the simple usage of external graphic state objects which allow you to define opacity values for stroking and non-stroking operations.
To simplify the demo we simply re-draw an image with different opacity values.
PHP
<?php
use setasign\SetaPDF2\Core\Document;
use setasign\SetaPDF2\Core\Image\Image;
use setasign\SetaPDF2\Core\PageFormats;
use setasign\SetaPDF2\Core\Resource\ExtGState;
use setasign\SetaPDF2\Core\Writer\HttpWriter;
// load and register the autoload function
require_once '../../../../../bootstrap.php';
// create a writer instance
$writer = new HttpWriter('transparency.pdf', true);
// create a document instance
$document = new Document($writer);
$pages = $document->getCatalog()->getPages();
$page = $pages->create(PageFormats::A4);
$image = Image::getByPath($assetsDirectory . '/images/fuchslocher/green-morning.jpg')->toXObject($document);
$canvas = $page->getCanvas();
$image->draw($canvas, 30, 600, 250);
// create a graphic state with opacity set to 0.7
$gs = new ExtGState();
$gs->setConstantOpacity(.7);
$gs->setConstantOpacityNonStroking(.7);
$gs->getIndirectObject($document);
// and draw the image
$canvas->saveGraphicState();
$canvas->setGraphicState($gs);
$image->draw($canvas, 60, 570, 250);
$canvas->restoreGraphicState();
// create a graphic state with opacity set to 0.4
$gs = new ExtGState();
$gs->setConstantOpacity(.4);
$gs->setConstantOpacityNonStroking(.4);
$gs->getIndirectObject($document);
// and draw the image
$canvas->saveGraphicState();
$canvas->setGraphicState($gs);
$image->draw($canvas, 90, 540, 250);
$canvas->restoreGraphicState();
// create a graphic state with opacity set to 0.1
$gs = new ExtGState();
$gs->setConstantOpacity(.1);
$gs->setConstantOpacityNonStroking(.1);
$gs->getIndirectObject($document);
// and draw the image
$canvas->saveGraphicState();
$canvas->setGraphicState($gs);
$image->draw($canvas, 120, 510, 250);
$canvas->restoreGraphicState();
// save and finish
$document->save()->finish();