[vtkusers] extract subset

[Ula Popov]

Hello all,

I know that there is a filter in paraview "extract subset".
I need to implement its functionality.

	vtkSmartPointer<vtkXMLImageDataReader> reader =
vtkSmartPointer<vtkXMLImageDataReader>::New();
	reader->SetFileName(filename);
	reader->Update();
	vtkImageData* grid = reader->GetOutput();

What function should I use? Can I apply it on image data (grid)?

Thank you,
Ula