function getImage()
{
  tfSXTxt = document.getElementById('tfSX').value;
  tfSYTxt = document.getElementById('tfSY').value;
  if(tfSXTxt == ""){
    alert("Prosz poda skal X.");
    return;
  }
  if(tfSYTxt == ""){
    alert("Prosz poda skal Y.");
    return;
  }

  url = "http://localhost/dane.php?sx=" + tfSXTxt;
  url += "&sy=" + tfSYTxt;
  url = encodeURI(url);

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