[vtkusers] image reader data spacing and IPW

[John Hunter]

I am reading in some CT data with a vtkVolume16Reader and visualizing
it with vtkImagePlaneWidgets.  The data are 512x512 by 91 slices and
the width and  height are 25cm and the slices are 0.1cm apart.
I am making the following call to set data spacing

     reader.SetDataSpacing(25.0/512, 25.0/512, 0.1)

but the planewidgets along the interpolated (slice) dimension appear a
little squished.  The CT is of the head, and the data are collected in
the transverse plane.  The sagital and coronal orientations of the
plane widgets appear compressed along the slice axis.

I am wondering if I am not setting the data spacing properly, or if I
am experiencing something unexpected from the vtkImageReslice
operations of the plane widget.  For example, if the reslicer
interpolates up to a larger numbr of slices slices, or something like
that, will the data spacing set in the reader be respected and scaled
appropriately?

Thanks,
John Hunter