procedure TSDIAppForm.ImageLibMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  midx: Integer;
  midy: Integer;
  r: Integer;
begin
  midx:=28;
  midy:=29;
  r:=24;
  if Sqr(midx-X)+Sqr(midy-Y)<=Sqr(r) then
      ShowMessage('Clicked');
end;