function getImage()
{
  tfAngleTxt = document.getElementById('tfAngle').value;
  if(tfAngleTxt == ""){
    alert("Prosz poda kt obrotu.");
    return;
  }

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

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