def _get_contour_values(min_val, max_val, base=0, interval=100):
    """Return a list of values between min and max within an interval."""
    i = base
    out = []
    if min_val < base:
        while i >= min_val:
            i -= interval
    while i <= max_val:
        if i >= min_val:
            out.append(i)
        i += interval
    return out
