[Insight-users] setting initial transform parameters

[Erik Türke]

Darren Weber schrieb:
>
>
> On Wed, Sep 9, 2009 at 6:17 AM, Luis Ibanez <luis.ibanez at kitware.com 
> <mailto:luis.ibanez at kitware.com>> wrote:
>
>     Hi Erik,
>
>     The BSplineTransform can be initilized directly with an
>     AffineTransform by simply connecting the AffineTransform
>     as its "Bulk" transform.
>
>     Please look at the examples:
>
>     Insight/Examples/Registration/
>               DeformableRegistration14.cxx
>               DeformableRegistration15.cxx
>               DeformableRegistration8.cxx
>
>
>     Look for the lines:
>
>      transform->SetBulkTransform( affine_transform );
>
>
>
> In the DeformableRegistration4.cxx, the BSpline transform creation, 
> intialization, and hook into the registration method looks something 
> like this:
>
> // Create a BSpline transform object.
> typedef itk::BSplineDeformableTransform<
>     CoordinateRepType,
>     SpaceDimension,
>     SplineOrder >  bsTransformType;
> bsTransformType::Pointer bsTransform = bsTransformType::New();
>
> // Initialize the BSpline transform parameters.
> typedef bsTransformType::bsParametersType bsParametersType;
> bsParametersType bsParameters( bsTransform->GetNumberOfParameters() );
> bsParameters.Fill( 0.0 );
> bsTransform->SetParameters( bsParameters );
>
> //  Pass the bsParameters into the registration method.
> bsRegistration->SetInitialTransformParameters( 
> bsTransform->GetParameters() );
>
>
> Given a prior affineTransform that will have a final transform from a 
> completed registration, could the above get replaced with:
>
>
> // Create a BSpline transform object.
> typedef itk::BSplineDeformableTransform<
>     CoordinateRepType,
>     SpaceDimension,
>     SplineOrder >  bsTransformType;
> bsTransformType::Pointer bsTransform = bsTransformType::New();
>
> // Initialize the BSpline transform parameters.
> bsTransform->SetBulkTransform( affineTransform );
>
> //  Pass the bsParameters into the registration method.
> bsRegistration->SetInitialTransformParameters( 
> bsTransform->GetParameters() );
>
>
>
> TIA,
> Darren
>
>
>
>  
>
>     ---
>
>     The general problem that you are facing, on the other hand,
>     does not have an easy solution. All Transforms have a
>     different number of parameters. This is simply because the
>     Transform hierarchy is progressively increasing the degrees
>     of freedom of the transforms.
>
>     You will have to initialize TransformA from TransfromB
>     on a case by case basis.
>
>
>     Regards,
>
>
>            Luis
>
>
>
>     ----------------------------------------------------------
>
>     On Tue, Sep 8, 2009 at 8:11 AM, Erik Tuerke <tuerke at cbs.mpg.de
>     <mailto:tuerke at cbs.mpg.de>> wrote:
>
>
>
>         Hello!
>
>         I am writing a registration programm based on itk.
>
>         I want the program to have the following facility: the user is
>         able to set a series of transforms. Considering an affine
>         transform following a non-linear transform(e.g. bspline
>         transform). What i want to do is to pass only the transform
>         gained by the affine transform to the bspline registration
>         step (not the resampled image from the affine registration step).
>         My problem is, that the regsitration method of the bspline
>         registration step expects a lot more parameters than i get by
>         the affine registration step. Is there a way to convert the
>         affine transform into a, say, bspline transform and pass this
>         transform to the SetInitialTransformParameters method of the
>         registration method which is responsible for the bspline
>         transform?
>
>
>         Thanks a lot and best regards!
>
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>
Hi!

Thanks for your reply to you, Luise and Darren!

For those, who wants to know the solution for passing a linear transform 
for initialize purpose to a different linear transform:

transformA->SetTranslation(transformB->GetTranslation);
transformA->SetMatrix(transformB->GetMatrix);

As yet this works fine for me.

Regards, Erik!