            writer = vtkBMPWriter()
        elif ext == '.jpg':
            writer = vtkJPEGWriter()
        elif ext == '.pnm':
            writer = vtkPNMWriter()
        elif ext == '.ps':
--
            writer = vtkBMPWriter()
        elif ext == '.jpg':
            writer = vtkJPEGWriter()
        elif ext == '.pnm':
            writer = vtkPNMWriter()
        elif ext == '.ps':
