def split(arr):
    """
    Split array into four equal quadrants
    """
    mid_x, mid_y = arr.shape[0] // 2, arr.shape[1] // 2
    q1 = arr[0:mid_x, 0:mid_y]
    q2 = arr[0:mid_x, mid_y::]
    q3 = arr[mid_x::, 0:mid_y]
    q4 = arr[mid_x::, mid_y::]
    return q1, q2, q3, q4