[vtkusers] How to convert vtkImageCast back to vtkImageData

[Quentan Qi]

Hi there,

After casting an image using vtkImageCast, it becomes a vtkImageCast object, but I want to use vtkImplicitVolume which requires vtkImageData type. How to convert vtkImageCast back to vtkImageData?

```Python

reader = read_DICOM(path_dicom)  # result is a vtkImageData

cast = vtk.vtkImageCast()
cast.SetInputData(reader)  # vtkImageData —> vtkImageCast
cast.SetOutputScalarTypeToShort()  # I need this type

implicit_volume = vtk.vtkImplicitVolume()
implicit_volume.SetVolume(reader)  # It works but I need “cast” instead
# implicit_volume.SetVolume(cast)  # It’s wrong because vtkImageData is required, but a vtkImageCast was given
# other things

```

Thanks a lot!

Cheers,
Quentan