如何使用Apache PDFBox将.png图像添加到pdf

当我尝试使用pdfBox绘制png图像时，页面保持空白。有没有办法使用pdfBox插入png图像？

public void createPDFFromImage( String inputFile, String image, String outputFile ) 
        throws IOException, COSVisitorException
{
    // the document
    PDDocument doc = null;
    try
    {
        doc = PDDocument.load( inputFile );

        //we will add the image to the first page.
        PDPage page = (PDPage)doc.getDocumentCatalog().getAllPages().get( 0 );

        PDXObjectImage ximage = null;
        if( image.toLowerCase().endsWith( ".jpg" ) )
        {
            ximage = new PDJpeg(doc, new FileInputStream( image ) );
        }
        else if (image.toLowerCase().endsWith(".tif") || image.toLowerCase().endsWith(".tiff"))
        {
            ximage = new PDCcitt(doc, new RandomAccessFile(new File(image),"r"));
        }
        else
        {
            BufferedImage awtImage = ImageIO.read( new File( image ) );
            ximage = new PDPixelMap(doc, awtImage);
  //          throw new IOException( "Image type not supported:" + image );
        }
        PDPageContentStream contentStream = new PDPageContentStream(doc, page, true, true);
        contentStream.drawImage( ximage, 20, 20 );
        contentStream.close();
        doc.save( outputFile );
    }
    finally
    {
        if( doc != null )
        {
            doc.close();
        }
    }
}