Merge image in Java

Presentation pres = new Presentation();
try {
    IPPImage image1 = pres.getImages().addImage(Files.readAllBytes("image1.png"));
    pres.getSlides().get_Item(0).getShapes().addPictureFrame(ShapeType.Rectangle, 0, 0, 100, 100, image1);

    IPPImage image2 = pres.getImages().addImage(Files.readAllBytes("image2.png"));
    pres.getSlides().get_Item(0).getShapes().addPictureFrame(ShapeType.Rectangle, 0, 200, 100, 100, image2);

    for (int index = 0; index < pres.getSlides().size(); index++)
    {
        ISlide slide = pres.getSlides().get_Item(index);
        BufferedImage bufferedImage = slide.getThumbnail();
        ImageIO.write(bufferedImage, "PNG", new File("image_java_" + index + ".png"));
    }
} finally {
    if (pres != null) pres.dispose();
}