[Insight-users] Applying an affine to an image with a special twist.

[Peter Lorenzen]

Hi All,

In the ITK examples directory there are several well documented 
examples of how to translate an image to some origin, apply a rotation, 
and translate back from said origin.

I would like to do the same thing, except I would like to replace the 
rotation part with the application of an affine.

For example, consider the following code snippet:

   //////////////////////////////////////////////
   // Translate centroid to the origin in (mm) //
   //////////////////////////////////////////////
   TransformType::OutputVectorType translateCentroidToOrigin;
   translateCentroidToOrigin[0] = -centroidX * imageSpacing[0];
   translateCentroidToOrigin[1] = -centroidY * imageSpacing[1];
   translateCentroidToOrigin[2] = -centroidZ * imageSpacing[2];
   transform->Translate( translateCentroidToOrigin );

   //////////////////////
   // Apply the affine //
   //////////////////////
   transform->SetMatrix( matrix );
   transform->SetOffset( offset );
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I can apply this affine, but I end up blowing away the original 
translation of the
centroid to the origin.

   ////////////////////////////////////////////////
   // Translate centroid from the origin in (mm) //
   ////////////////////////////////////////////////
   TransformType::OutputVectorType translateCentroidFromOrigin;
   translateCentroidFromOrigin[0] = centroidX * imageSpacing[0];
   translateCentroidFromOrigin[1] = centroidY * imageSpacing[1];
   translateCentroidFromOrigin[2] = centroidZ * imageSpacing[2];
   transform->Translate( translateCentroidFromOrigin );


Is there a way I can do this in ITK without having to generate two 
additional images (i.e. decouple with transformation into three 
separate stages)?


Thanks!

- Peter

--
Peter J. Lorenzen
Ph.D. Student
Department of Computer Science
University of North Carolina at Chapel Hill
Sitterson Hall 268, Campus Box 3175
Chapel Hill, NC  27599-3175

TEL (919) 962-1879
FAX (919) 962-1699
E-MAIL lorenzen at cs . unc . edu
WEB PAGE http://www . cs . unc . edu/~lorenzen