PHPでPDFをBMPに変換する

<?php
require_once("http://localhost:8080/JavaBridge/java/Java.inc");
require_once("lib/aspose.slides.php");
 
use aspose\slides\Presentation;
use aspose\slides\SaveFormat;
 
$pres = new Presentation();
try
{
    $pres->getSlides()->removeAt(0);
    $pres->getSlides()->addFromPdf("document.pdf");
    for ($i = 0; $i < java_values($pres->getSlides()->size()); $i++)
    {
        $bmp = $pres->getSlides()->get_Item($i)->getThumbnail(2, 2);
        $imageio = new Java("javax.imageio.ImageIO");
        $javafile = new Java("java.io.File", "slide_". $i .".bmp");
        $imageio->write($bmp, "BMP", $javafile);
    }
}
finally
{
    if ($pres != null) $pres->dispose();
}
?>