function getImage()
{
  if(document.getElementById('rb1').checked){
    param = "1";
  }
  else if(document.getElementById('rb2').checked){
    param = "2";
  }
  else if(document.getElementById('rb3').checked){
    param = "3";
  }
  else if(document.getElementById('rb4').checked){
    param = "4";
  }
  else{
    alert('Prosz zaznaczy jedn z opcji.');
  }

  url = "http://localhost/dane.php?filtr=" + param;
  url = encodeURI(url);

  var btnWykonaj = document.getElementById('btnWykonaj');
  btnWykonaj.disabled = true;
  startGETRequest(url, onComplete, onEnd);
}