'Test using a specified linear stretch'

def test_linear(self):

    map = lupton_rgb.LinearMapping((-8.45), 13.44)
    rgbImage = map.make_rgb_image(self.image_r, self.image_g, self.image_b)
    if display:
        display_rgb(rgbImage, title=sys._getframe().f_code.co_name)
