Transparency with colourmaps

[Andrew Sullivan]

I've got a chemical simulation running that I'm visualizing with a colormap:

colourMapChemical = glumpy.colormap.Colormap("orange",

                                (0.00, (1.0, 0.6, 0.2)),

                                (1.00, (1.0, 1.0, 1.0)))

image = glumpy.image.Image(v, interpolation = 'nearest', colormap = colourMapChemical)

But the simulation only exists within some arbitrarily shaped boundary, specified in a 2 dimensional numpy array. I want to be able to draw this boundary over the top of the simulation and this requires transparency, but I can't get it working, I just end up with the colours of the boundary layer on my screen. This is the pertinent code: 

figure = glumpy.figure((m * scaleFactor, n * scaleFactor))

colourMapChemical = glumpy.colormap.Colormap("orange",

                                (0.00, (1.0, 0.6, 0.2)),

                                (1.00, (1.0, 1.0, 1.0)))

image = glumpy.image.Image(v, interpolation = 'nearest', colormap = colourMapChemical)

colourMapBoundaries = glumpy.colormap.Colormap("Boundries",

                                (0.00, (1.0, 0.1, 0.0, 1.0)),

                                (1.00, (1.0, 0.0, 1.0, 0.0)))

image2= glumpy.image.Image(areaInSimulation, interpolation = 'nearest', colormap = colourMapBoundaries)

@figure.event

def on_draw():

    figure.clear()

    

    OpenGL.GL.glEnable( OpenGL.GL.GL_BLEND ) 

    OpenGL.GL.glBlendFunc( OpenGL.GL.GL_SRC_ALPHA, OpenGL.GL.GL_ONE_MINUS_SRC_ALPHA )

    

    #mage2.draw( x=0, y=0, z=1, width=figure.width, height=figure.height )

    image.draw( x=0, y=0, z=0, width=figure.width, height=figure.height )

    

dt = 0.1

@figure.event

def on_idle(elapsed):

    global u,v,U,V,Z,F,k, diffusionConstants

    for i in range(10):

        Lu = (K*U.ravel()).reshape(U.shape)

        Lv = (K*V.ravel()).reshape(V.shape)

        u += dt * (diffusionConstants[0]*Lu - Z +  f   *(1-U))

        v += dt * (diffusionConstants[1]*Lv + Z - (f+k)*V    )

        U,V = u, v

        Z = U*V*V

    image2.update()

    image.update()

    figure.redraw()

glumpy.show()

Any suggestions on what I'm doing wrong?