[vtkusers] error when connecting ITK with VTK

[David Doria]

> ERROR: In C:\APIs\VTK\vtk-5.8.0\Imaging\vtkImageImport.cxx, line 338
> vtkImageImport (0000000003395080): Calling UpdateInformationCallback:
> c:\apis\itk\insighttoolkit-3.20.0\code\basicfilters\itkVTKImageImport.txx:241:
> itk::ERROR: VTKImageImport(00000000034AB3E0): Input number of components is
> 4 but should be 1

Did you call

imageImport->SetNumberOfScalarComponents (4);

?