def compare_bounds(b0, b1):
    """
    Function that compares two bounds with each other. Returns the max bound.

    Parameters
    ----------
    b0 : tuple
        tuple of xmin, ymin, xmax, ymax
    b1 : tuple
        tuple of xmin, ymin, xmax, ymax        

    Returns
    -------
    tuple
        min of mins and max of maxs
    """
    if len(b0) and len(b1):
        bounds = min(b0[0], b1[0]), min(b0[1], b1[1]), max(b0[2], b1[2]), max(
            b0[3], b1[3])
    elif len(b0) and not len(b1):
        bounds = b0
    elif not len(b0) and len(b1):
        bounds = b1
    else:
        bounds = []
    return bounds
