Fusionar imagen en PHP

<?php
require_once("http://localhost:8080/JavaBridge/java/Java.inc");
require_once("lib/aspose.slides.php");

$pres = new Presentation();
try
{
    $pres->getSlides()->removeAt(0);
    
    $filename1 = 'file1.html';
    $f1 = fopen($filename1, 'r');
    if ($f1) {
        $contents1 = fread($f1, filesize($filename1));
        fclose($f1);
    }
    
    $pres->getSlides()->addFromHtml($contents1);
    
    $filename2 = 'file2.html';
    $f2 = fopen($filename2, 'r');
    if ($f2) {
        $contents2 = fread($f2, filesize($filename2));
        fclose($f2);
    }
    
    $pres->getSlides()->addFromHtml($contents2);

    $img = $pres->getSlides()->get_Item(0)->getThumbnail(2, 2);
    $imageio = new Java("javax.imageio.ImageIO");
    $javafile = new Java("java.io.File", "merged-image.png");
    $imageio->write($img, "PNG", $javafile);
}
finally
{
    if ($pres != null) $pres->dispose();
}
?>