title: How to watermark image in pdf exported in datatable
body: <p>I am using datatables to display data in table format and have given export option , to export data into csv , pdf . Now i want to add a watermark image into pdf that gets downloaded from button in data table.</p>
  
  <p>Here is code i tried but it didnt work for me,</p>
  
  <pre><code>var table = $('#holiday').DataTable( {
                      "dom": '&lt;"nav" B&gt;lfrtip',
                      "buttons": [
                                  'excelHtml5',
                                  'csvHtml5',
                                  {
                                      extend: 'pdfHtml5',
                                      customize: function ( doc ) {
                                      doc.content.splice( 1, 0, {
                                            margin: [ 20, 20, 20, 20 ],
                                            alignment: 'center',
                                            image:'data:image/png;base64,abcdddd'
                                  }]  });
  </code></pre>
  
  <p>I also tried using watermark in place of image , but i didnt get result. Please help me regarding this. Thanks in advance                             </p>