[vtkusers] 2's complement

[Raúl Ferriz]

Thanks for your answer!

What I'm trying to do is that all DICOM's that I have (with MONOCHROME2) 
could be displayed with black background and white foreground. Currently 
only dicoms with Pixel Representation = 0 are displayed as this way, and 
dicoms with Pixel Representation = 1(this means that values are stored 
in 2's complement)  are displayed with  white background and black 
foreground.

Now I will try with vtkImageShiftScale, may be this is enought to get 
what I want.

Many thanks again.