'Return an RGB(A) lookup table (ndarray).
**Arguments:**
start             The starting value in the lookup table (default=0.0)
stop              The final value in the lookup table (default=1.0)
nPts              The number of points in the returned lookup table.
alpha             True, False, or None - Specifies whether or not alpha values are included
in the table. If alpha is None, it will be automatically determined.
mode              Determines return type: \'byte\' (0-255), \'float\' (0.0-1.0), or \'qcolor\'.
See :func:`map() <pyqtgraph.ColorMap.map>`.'

def getLookupTable(self, start=0.0, stop=1.0, nPts=512, alpha=None, mode='byte'):

    if isinstance(mode, basestring):
        mode = self.enumMap[mode.lower()]
    if (alpha is None):
        alpha = self.usesAlpha()
    x = np.linspace(start, stop, nPts)
    table = self.map(x, mode)
    if (not alpha):
        return table[:, :3]
    else:
        return table
