Apache POI method "addPicture" doesn't work for me

I am having a problem inserting an image into an Excel workbook with Apache POI (version 3.7). Here's my code:

private static void createAndFillWorkbook() {
    FileOutputStream out = null;
    FileInputStream in = null;
    try {
        HSSFWorkbook workbook = new HSSFWorkbook();
        File picture = new File("D:\\pngPict.png");
        byte[] buf = new byte[(int) picture.length()];
        in = new FileInputStream(picture);
        in.read(buf);
        workbook.addPicture(buf, Workbook.PICTURE_TYPE_PNG);
        out = new FileOutputStream("D:\\Book3.xls");
        workbook.write(out);
    } catch (Exception e) {
    } finally {
        try {
            if (out != null) {
                out.close();
            }
            if (in != null) {
                in.close();
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

      

        
        
        
      

    

It doesn't work (I'm using the .xls file format) and I'm not sure why.