[Insight-users] Question about BSplineDeformableTransform

[Luis Ibanez]

Hi Wenjia,

As you have already pointed out, unfortunately the use of the 
SetCoefficientImage() method is not a suitable mechanism for
initializing the BSplineDeformableTransform when you plan to
use it in the Image Registration framework.

Probably your best option is to use image iterators in order
to visit each one of the coefficient images and copy their values
in the parameters array, then set that array by using the
SetParametes() method.


    Regards,


       Luis


---------------
wenjia wrote:
> Hello, everyone,
> 
> I am using ITK to do some B-spline deformable registration work. I 
> followed the examples given by ITK User's Guide and modified the code a 
> bit. Now I have got a question about setting the B-spline coefficients.
> 
> It is said in the documentation there are two ways setting the 
> coefficients, either by a vector parameter or an array of images. I 
> choosed the second option,
> 
> transform->SetCoefficientImages( images );
> 
> Then I need to set initial parameters for the registration method, 
> according to the examples,
> 
> registration->SetInitialTransformParameters( transform->GetParameters() );
> 
> However, transform->GetParameters() seems to return a NULL pointer.
> 
> The reason is that when transform->SetCoefficientImages( images ) is 
> performed, m_InputParametersPointer is set NULL. What 
> transform->GetParameters() returns is just (*m_InputParametersPointer).
> 
> Another question is that in this way, the Jacobian matrix is not 
> allocated memory to. So we can not GetJacobian() either.
> 
> The SetCoefficientImage() function is attached. Thanks for your reading.
> 
> Cheers,
> Wenjia
> 
> 
> // Set the B-Spline coefficients using input images
> template<class TScalarType, unsigned int NDimensions, unsigned int 
> VSplineOrder>
> void
> BSplineDeformableTransform<TScalarType, NDimensions,VSplineOrder>
> ::SetCoefficientImage( ImagePointer images[] )
> {
>   if ( images[0] )
>     {
>     this->SetGridRegion( images[0]->GetBufferedRegion() );
>     this->SetGridSpacing( images[0]->GetSpacing() );
>     this->SetGridOrigin( images[0]->GetOrigin() );
> 
>     for( unsigned int j = 0; j < SpaceDimension; j++ )
>       {
>       m_CoefficientImage[j] = images[j];
>       }
> 
>     // Clean up buffered parameters
>     m_InternalParametersBuffer = ParametersType( 0 );
>     m_InputParametersPointer  = NULL;
> 
>     }
> 
> }
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