[vtkusers] how to use vtkImagePlaneWidget to display a image of unsinged char?

[kdsfinger at gmail.com]

hi, all
I have a stack of images (png file of unsigned char) and I have import
them into vtk using vtkPNGReader. I was expecting that the value of 0
is full black and 255 is full white. However, the display of the image
is very strange. It looks like a binary image after thresholding. And,
if you use the mouse interaction to adjust the color (saturation or
intensity? not sure), then it looks like you are change the threshold
of the binary image. Although the reading of the pixel value of the
image are all correct.
The example came with the vtk package under the Widgets dir all work
fine (the input of the vtkImagePlaneWidget is of 4bytes other than
1byte). If the vtkImagePlaneWidget can only display 4byte image
correct, is there some easy way to cast the 1byte data into 4bytes?
Thanks for help.

zl2k