[vtkusers] Matching two vtkImageData

[Tony]

Dear listers 

I have two vtkImageData classes, they are on the same axes but 
have different resolutions and spatial extents. I am trying to 
rescale/resample each image to have the same spatial extent (cropping 
the larger image to match the smaller of the two images) and the same 
resolution as the higher resolution image (via interpolation). I have 
tried various combinations of methods but nothing seems to do what I 
want. Is there a simple combination of resize-ing and reslice-ing (or 
something I've missed) that will achieve this. The aim here is to 
perform quantitative analysis of the images so if vtk provides some 
better way of doing this without creating matching images first then I 
could skip this step. 

Thanks.