[Python] Project PNG image data as texture on plane in vtk

I have been trying to visualize in Python an image as a partially translucent texture on a plane in VTK.

My approach is to use vtkThresholdTextureCoords() to set the transparency based on the image values. However, I am struggling to apply the threshold. The error message states that there are no scalar data to texture threshold.

Thank you for any help!

Here is the code snippet:

def main():
#fileName = get_program_parameters()
fileName = 'ice.png'


readerFactory = vtkImageReader2Factory()
textureFile = readerFactory.CreateImageReader2(fileName)
textureFile.SetFileName(fileName)
textureFile.Update()


texture = vtkTexture()
texture.SetInputConnection(textureFile.GetOutputPort())
texture.InterpolateOn()


plane = vtkPlaneSource()
plane.SetCenter(0.0,0.0,0.0)
plane.SetNormal(0.0,1.0,0.0)

texturePlane = vtk.vtkTextureMapToPlane()
texturePlane.SetInputConnection(plane.GetOutputPort())



thresh = vtkThresholdTextureCoords()
thresh.SetInputConnection(texturePlane.GetOutputPort())
thresh.ThresholdByUpper(0.1)




planeMapper = vtkPolyDataMapper()
planeMapper.SetInputConnection(thresh.GetOutputPort())
#planeMapper.SetInputConnection(plane.GetOutputPort()) # This does work
planeMapper.SetScalarRange(textureFile.GetOutput().GetScalarRange())

planeActor = vtkActor()
planeActor.SetMapper(planeMapper)
planeActor.SetTexture(texture)




# Create the RenderWindow, Renderer and Interactor.
renderer = vtkRenderer()
renWin = vtkRenderWindow()
renWin.AddRenderer(renderer)
iren = vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)

# Add the actors to the renderer, set the background and size.
renderer.AddActor(planeActor)
colors = vtkNamedColors()
renderer.SetBackground(colors.GetColor3d('DarkSlateGray'))

renWin.SetSize(640, 480)
renWin.SetWindowName('TexturePlane')

# render the image
renWin.Render()

renderer.ResetCamera()
renderer.GetActiveCamera().Elevation(-30)
renderer.GetActiveCamera().Roll(-20)
renderer.ResetCameraClippingRange()
renWin.Render()
iren.Start()




return

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