def image_click_yshift(axes = "gca"):
    """
    Takes a starting and ending point, then shifts the image y by this amount
    """
    if axes == "gca": axes = _pylab.gca()

    try:
        p1 = _pylab.ginput()
        p2 = _pylab.ginput()

        yshift = p2[0][1]-p1[0][1]

        e = axes.images[0].get_extent()

        e[2] = e[2] + yshift
        e[3] = e[3] + yshift

        axes.images[0].set_extent(e)

        _pylab.draw()
    except:
        print("whoops")