[vtkusers] How to set RenderWindow in vtkImageView

[Jianlong Zhou]

hi, all
I have 4 render window in my application, for example, renWin1, 
renWin2, renWin3, and renWin4. The renWin4 is rendered to display 
2D slices and I want to use vtkImageView to render in it. But how to set 
render window in vtkImageView? I notice that vtkImageViewer has no 
this member function, only use Render() function. 

Thank you in advance.
Best regards,

Jianlong