[Insight-users] Re: Deformation Field Iterator Type

[Luis Ibanez]

Hi Kevin,


Please read the ITK Software Guide

      http://www.itk.org/ItkSoftwareGuide.pdf

In particular, Chapter 11, "Iterators" in pdf-pages 733-776.



Iterators will give you their current position in the
image grid when you call the "GetIndex()" method.


Then you can pass this Index() to the image in order to
compute the position of the iterator in physical space.

This can be done with code such as:


   itk::Point<float,3> it2point;

   vectorImage3D1->TransfromIndexToPhysicalPoint(
                          it2.GetIndex(), it2point );


---------

BTW: Your lines:

 >     vector3D1 = it2.Get();
 >     vector3D2[0] = vector3D1[0];
 >     vector3D2[1] = vector3D1[1];
 >     vector3D2[2] = vector3D1[2];
 >     it3.Set( vector3D2 );


can be reduced to


           it3.Set( it2.Get() );


ITK Vectors and points provide an assignment operator,
so you don't need to copy the components one by one.




   Regards,


      Luis


--------------------
Kevin Ming wrote:
> Hi Luis,
> 
> I've extended the Level Set deformable registration algorithm from 2D to 
> the 3D case, including the deformation field generation.  How would I go 
> about accessing each of the voxels in the image, then accessing each of 
> the 3 vector components within each voxel?  I know it has something to 
> do with the iterator, as coded below:
> 
> typedef itk::ImageRegionConstIterator< VectorImage3D1Type > Iterator3D1Type;
> 
>   typedef itk::ImageRegionIterator< VectorImage3D2Type > Iterator3D2Type;
> 
>   Iterator3D1Type  it2( vectorImage3D1, region3D1 );
>   Iterator3D2Type  it3( vectorImage3D2, region3D2 );
> 
>   it2.GoToBegin();
>   it3.GoToBegin();
> 
>   Vector3D1Type vector3D1;
>   Vector3D2Type vector3D2;
> 
>   while( !it2.IsAtEnd() )
>     {
>     vector3D1 = it2.Get();
>     vector3D2[0] = vector3D1[0]; 
>     vector3D2[1] = vector3D1[1]; 
>     vector3D2[2] = vector3D1[2];
>     it3.Set( vector3D2 );
>     ++it2;
>     ++it3;
>     }
> 
> But how do I know which voxel the iterator is on (ie. where it is in the 
> image, in x,y,z components), especially when it's in 3D?
> 
> 
> Thank you,
> Kevin