plotting streamlines from stream2

A simple reading of the help files suggests that this will work.

    [Gx, Gy] = imgradientxy(uint8(filteredreducedSection), 'CentralDifference');
  figure (4)
     XY = stream2(Gx,Gy,X,Y);
   streamline(XY)

But I just get a blank grid. I know that Gx and Gy are created because I can create a quiver plot from them. thoughts?