[vtkusers] alpha transparency: image to texture

[Jan Vittrup Hansen]

Hi,

  I need to map some monochrome texturemaps with the output from a rendering
of a sphere. This I've managed to do by straight application of the
vtkWindowToImageFilter. Only the background is included in the texturemap,
where I'd much rather have transparency. Naively I tried the following approach
only to get a core dump when I try to render using the map - am I missing
something? (btw: I try to create a monochrome image with alpha transparency -
i.e. 2 bytes per pixel)

 Regards, Jan...
...
    filter = vtkWindowToImageFilter()
    filter.SetInput(renderWindow)
 
    image = vtkImageAppendComponents()
    image.SetInput1(filter.GetOutput())
    image.SetInput2(filter.GetOutput())

    return image.GetOutput()
...