Extracting images from pptx with apache poi discarding charts

Question

I am trying to convert pptx to png or pdf with apache poi but after conversion all charts are discarded. I want all charts also in my converted png or pdf.

version: Apache POI 3.16

 public void convertPPTXtoImg() throws IOException, DocumentException, InvalidFormatException {
    FileInputStream inputStream = new FileInputStream("vzw.pptx");

    XMLSlideShow ppt = new XMLSlideShow(OPCPackage.open(inputStream));

    inputStream.close();
    Dimension pgsize = ppt.getPageSize();
    float scale = 1;
    int width = (int) (pgsize.width * scale);
    int height = (int) (pgsize.height * scale);

    int i = 1;
    int totalSlides = ppt.getSlides().size();

           for (XSLFSlide slide : ppt.getSlides()) {

                BufferedImage img = new BufferedImage(pgsize.width, pgsize.height,
                        BufferedImage.TYPE_INT_RGB);
                Graphics2D graphics = img.createGraphics();
                graphics.setPaint(Color.white);
                graphics.fill(new Rectangle2D.Float(0, 0, pgsize.width,
                        pgsize.height));
                graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                graphics.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
                graphics.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
                graphics.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
                graphics.setColor(Color.white);
                graphics.clearRect(0, 0, width, height);
                graphics.scale(scale, scale);

                slide.draw(graphics);
                FileOutputStream out = new FileOutputStream("images/"+i+".png");
                javax.imageio.ImageIO.write(img, "png", out);
                out.close();
                i++;
           }
  }