def get_index_value(self, y):
            return min(1.0, max(0.0, 1.0 - float(y-1)/(self.control.height-1)))
Get value in [0..1] of height index y
dataset/ETHPy150Open enthought/mayavi/tvtk/util/tk_gradient_editor.py/FunctionControl.Channel.get_index_value