[vtkusers] vtklookuptable question

[kdsfinger at gmail.com]

hi, all
I have a vtkImageData built on a stack images imported by
vtkPNGReader. When I display it by the vtkImagePlaneWidget, it has
only 2 colors: the 0 values are mapped to black and all the rest are
mapped to white. The values in the vtkImageData are grayscale
(unsigned char, a mri brain image). I tried some setting of the
vtkLookupTable but did not success. Any suggestions?
zl2k