vtkImageActor example

import vtk
import math

red = [255,0,0]
blue= [0,0,255]
green= [0,255,0]
black= [0,0,0]

ren = vtk.vtkRenderer()
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren)

iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)
interactorstyle = iren.GetInteractorStyle()
interactorstyle.SetCurrentStyleToTrackballCamera()

camera = vtk.vtkCamera()
camera.SetClippingRange(-10, 500)
camera.SetPosition(0, -1, 3000)
camera.SetFocalPoint(255, 255, 0)

#camera.SetViewAngle(50)
#camera.SetViewUp(1, 1, 0)
ren.SetActiveCamera(camera)


# first image
vol = vtk.vtkImageData()
vol.SetDimensions(512,512,1)
vol.SetSpacing(1,1,1)
vol.SetOrigin(0,0,0)
vol.AllocateScalars()
vol.SetNumberOfScalarComponents(3)
vol.SetScalarTypeToUnsignedChar()
# initialize the image
scalars = vtk.vtkCharArray()
for n in range(512):
    for m in range(512):
        x = 512/2 -n
        y = 512/2 -m
        d = math.sqrt(x*x+y*y)
        if ( d < 100 ):
            col = red
        elif (d<200):
            col = green
        else:
            col = blue
        for c in range(3):
            scalars.InsertTuple1( n*(512*3) + m*3 +c, col[c] )

vol.GetPointData().SetScalars(scalars)
vol.Update()
ia = vtk.vtkImageActor()
ia.SetInput(vol)
ia.InterpolateOff()
#then add it to the renderer
ren.AddActor(ia)

# with renWin.Render() the update (below) will not be shown
#renWin.Render()
# with ren.Render() the update will show
ren.Render()

# now modify the image
for n in range(512):
    for m in range(512):
        x = 512/2 -n
        y = 512/2 -m
        d = math.sqrt(x*x+y*y)
        if ( d < 66 ):
            col = black
            for c in range(3):
                scalars.SetValue( n*(512*3) + m*3 +c, chr(col[c]) )
vol.Update()


iren.Initialize()
iren.Start()