[vtkusers] vtkImagePermute without copying the data

[John Biddiscombe]

>If you use 3D textures (VTK doesn't... anyone have some spare time to add
>them?) then everything can be done in memory, although you have to convert

Just think what fun you could have redoing all the raycast mappers to 
permute the axes too!
....
actually, a class like vtkImagePermute which only acted as an access 
function might just cope. You could have a meta-dataobject which 
"contained" a real data object and supplied new GetPixel type operations, 
such that the axes were permuted. This could have a vtkImageData object 
embedded in it, but not duplicate the memory. It'd be quite interesting 
because then you could override the Get(index) operations arbitrarily and 
it'd be a new kind of mapper in a way. (Magnification, scaling, 
shearing...permuting could all be simulated by changing the indexing scheme 
into the underlying data - what a pain).


JB