NullPointerException when reading a GIF file with a transparent color

public void generatePDF() throws IOException,COSVisitorException,FileNotFoundException
	{
		PDDocument report_pdf = new PDDocument();
		PDPage pdfpage1 = new PDPage(PDPage.PAGE_SIZE_LETTER);
		PDRectangle text_dimensions = pdfpage1.getMediaBox();
		PDXObjectImage pdfImage = null;
		PDPageContentStream stream = new PDPageContentStream(report_pdf, pdfpage1);
		stream.setFont(PDType1Font.HELVETICA, 30);
		stream.beginText();
		stream.moveTextPositionByAmount(130,text_dimensions.getHeight()-50);
		stream.drawString("Hello");
		stream.endText();
		BufferedImage awtImage = ImageIO.read(new File("/var/tmp/test1.gif"));
		 //pdfImage = new PDJpeg(report_pdf,awtImage);
		pdfImage = new PDPixelMap(report_pdf, awtImage);
		stream.drawImage(pdfImage, 60, 120 );
        //stream.drawXObject(pdfImage, 150, 400, pdfImage.getWidth()*10, pdfImage.getHeight()*20);
		stream.close();
		report_pdf.addPage(pdfpage1);
		report_pdf.save(new File("/var/tmp/report.pdf"));
	}

Exception in thread "main" java.lang.NullPointerException
	at org.apache.pdfbox.pdmodel.graphics.xobject.PDXObjectImage.extractAlphaImage(PDXObjectImage.java:499)
	at org.apache.pdfbox.pdmodel.graphics.xobject.PDPixelMap.createImageStream(PDPixelMap.java:122)
	at org.apache.pdfbox.pdmodel.graphics.xobject.PDPixelMap.<init>(PDPixelMap.java:86)
	at org.reports.ReportGenerator.ReportGenerator.generatePDF(ReportGenerator.java:122)