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Add inverse capability to KernelTransform #4529

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Add inverse capability to KernelTransform #4529

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19 changes: 19 additions & 0 deletions Modules/Core/Transform/include/itkKernelTransform.h
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Original file line number Diff line number Diff line change
Expand Up @@ -225,6 +225,25 @@ class ITK_TEMPLATE_EXPORT KernelTransform : public Transform<TParametersValueTyp
return Self::TransformCategoryEnum::Spline;
}

/** Returns a boolean indicating whether it is possible or not to compute the
* inverse of this current Transform. If it is possible, then the inverse of
* the transform is returned in the inverseTransform variable passed by the
* user. Inverting is possible if the variable is not a null pointer.
*/
bool
GetInverse(Self * inverseTransform) const;

using InverseTransformBasePointer = typename Superclass::InverseTransformBasePointer;

/** Return an inverse of this transform. */
InverseTransformBasePointer
GetInverseTransform() const override
{
Pointer inv = New();
this->GetInverse(inv);
return inv;
}

/** Stiffness of the spline. A stiffness of zero results in the
* standard interpolating spline. A non-zero stiffness allows the
* spline to approximate rather than interpolate the landmarks.
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37 changes: 37 additions & 0 deletions Modules/Core/Transform/include/itkKernelTransform.hxx
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Expand Up @@ -508,6 +508,43 @@ KernelTransform<TParametersValueType, VDimension>::GetFixedParameters() const ->
}


template <typename TParametersValueType, unsigned int VDimension>
bool
KernelTransform<TParametersValueType, VDimension>::GetInverse(Self * inverseTransform) const
{
if (!inverseTransform)
{
return false;
}

auto deepCopyLandmarks = [](const typename PointSetType::ConstPointer source,
typename PointSetType::Pointer destination) {
typename PointSetType::PointsContainer::ConstIterator sourceIt = source->GetPoints()->Begin();

typename PointSetType::PointIdentifier i{ 0 };
while (sourceIt != source->GetPoints()->End())
{
destination->SetPoint(i, sourceIt->Value());
++i;
++sourceIt;
}
};

// make a deep copy of the source and target landmarks
typename PointSetType::Pointer sourceLandmarks = PointSetType::New();
typename PointSetType::Pointer targetLandmarks = PointSetType::New();
Comment on lines +534 to +535
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Please consider using auto here. For the return type of Type::New() we have agreed that auto is appropriate: https://github.com/InsightSoftwareConsortium/ITKSoftwareGuide/blob/d1562dd6dbc929ba18fdf8ce8aa86e8337597d7e/SoftwareGuide/Latex/Appendices/CodingStyleGuide.tex#L1558-L1562

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const auto would be even nicer 😇

    const auto sourceLandmarks = PointSetType::New();
    const auto targetLandmarks = PointSetType::New();

deepCopyLandmarks(this->GetSourceLandmarks(), sourceLandmarks);
deepCopyLandmarks(this->GetTargetLandmarks(), targetLandmarks);
Comment on lines +536 to +537
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Please consider directly copying the internal STL containers of the landmarks:

  sourceLandmarks->GetPoints()->CastToSTLContainer() =
    m_SourceLandmarks->GetPoints()->CastToSTLConstContainer();
  targetLandmarks->GetPoints()->CastToSTLContainer() =
    m_TargetLandmarks->GetPoints()->CastToSTLConstContainer();


// inversion comes from reversing the landmarks
inverseTransform->SetSourceLandmarks(targetLandmarks);
inverseTransform->SetTargetLandmarks(sourceLandmarks);
inverseTransform->SetStiffness(this->GetStiffness());
Comment on lines +540 to +542
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I think it's OK for a class to directly access its own data members, without calling Get and Set. So more like:

  inverseTransform->m_SourceLandmarks = targetLandmarks;
  inverseTransform->m_TargetLandmarks = sourceLandmarks;
  inverseTransform->m_Stiffness = m_Stiffness;

Right?

inverseTransform->ComputeWMatrix();

return true;
}

template <typename TParametersValueType, unsigned int VDimension>
void
KernelTransform<TParametersValueType, VDimension>::PrintSelf(std::ostream & os, Indent indent) const
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