WriteReadVtkImageData

import vtk

filename = "writeImageData.vti"

imageData = vtk.vtkImageData()
imageData.SetDimensions(3, 4, 5)
if vtk.VTK_MAJOR_VERSION <= 5:
    imageData.SetNumberOfScalarComponents(1)
    imageData.SetScalarTypeToDouble()
else:
    imageData.AllocateScalars(vtk.VTK_DOUBLE, 1)

dims = imageData.GetDimensions()

# Fill every entry of the image data with "2.0"
for z in range(dims[2]):
    for y in range(dims[1]):
        for x in range(dims[0]):
            imageData.SetScalarComponentFromDouble(x, y, z, 0, 2.0)

writer = vtk.vtkXMLImageDataWriter()
writer.SetFileName(filename)
if vtk.VTK_MAJOR_VERSION <= 5:
    writer.SetInputConnection(imageData.GetProducerPort())
else:
    writer.SetInputData(imageData)
writer.Write()

# Read the file (to test that it was written correctly)
reader = vtk.vtkXMLImageDataReader()
reader.SetFileName(filename)
reader.Update()

# Convert the image to a polydata
imageDataGeometryFilter = vtk.vtkImageDataGeometryFilter()
imageDataGeometryFilter.SetInputConnection(reader.GetOutputPort())
imageDataGeometryFilter.Update()

mapper = vtk.vtkPolyDataMapper()
mapper.SetInputConnection(imageDataGeometryFilter.GetOutputPort())

actor = vtk.vtkActor()
actor.SetMapper(mapper)
actor.GetProperty().SetPointSize(3)

# Setup rendering
renderer = vtk.vtkRenderer()
renderer.AddActor(actor)
renderer.SetBackground(1, 1, 1)
renderer.ResetCamera()

renderWindow = vtk.vtkRenderWindow()
renderWindow.AddRenderer(renderer)

renderWindowInteractor = vtk.vtkRenderWindowInteractor()

renderWindowInteractor.SetRenderWindow(renderWindow)
renderWindowInteractor.Initialize()
renderWindowInteractor.Start()