def METHOD_NAME(ar1, ar2, corrPower=1):
    """
        Determine the relative shift between a pair of arrays giving the best overlap.
        Shift determination uses the brightest pixel in the cross correlation, and is
    thus limited to pixel resolution. corrPower specifies the cross correlation
    power, with 1 corresponding to a cross correlation and 0 a phase correlation.
        Args:
                ar1,ar2 (2D ndarrays):
        corrPower (float between 0 and 1, inclusive): 1=cross correlation, 0=phase
            correlation
    Returns:
                (2-tuple): (shiftx,shifty) - the relative image shift, in pixels
    """
    cc = get_cross_correlation(ar1, ar2, corrPower)
    xshift, yshift = np.unravel_index(np.argmax(cc), ar1.shape)
    return xshift, yshift