itkIdentityTransform.h

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/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkIdentityTransform_h
#define itkIdentityTransform_h
 
#include "itkObject.h"
#include "itkPoint.h"
#include "itkCovariantVector.h"
#include "vnl/vnl_vector_fixed.h"
#include "itkArray2D.h"
#include "itkTransform.h"
 
namespace itk
{
template <typename TParametersValueType, unsigned int NDimensions = 3>
class ITK_TEMPLATE_EXPORT IdentityTransform : public Transform<TParametersValueType, NDimensions, NDimensions>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(IdentityTransform);
 
  using Self = IdentityTransform;
  using Superclass = Transform<TParametersValueType, NDimensions, NDimensions>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;
 
  itkNewMacro(Self);
 
  itkTypeMacro(IdentityTransform, Transform);
 
  static constexpr unsigned int InputSpaceDimension = NDimensions;
  static constexpr unsigned int OutputSpaceDimension = NDimensions;
 
  using ParametersType = typename Superclass::ParametersType;
  using ParametersValueType = typename Superclass::ParametersValueType;
  using FixedParametersType = typename Superclass::FixedParametersType;
  using FixedParametersValueType = typename Superclass::FixedParametersValueType;
  using ScalarType = ParametersValueType;
 
 
  using JacobianType = typename Superclass::JacobianType;
  using JacobianPositionType = typename Superclass::JacobianPositionType;
  using InverseJacobianPositionType = typename Superclass::InverseJacobianPositionType;
 
  using TransformCategoryEnum = typename Superclass::TransformCategoryEnum;
 
  using InputVectorType = Vector<TParametersValueType, Self::InputSpaceDimension>;
  using OutputVectorType = Vector<TParametersValueType, Self::OutputSpaceDimension>;
 
  using InputCovariantVectorType = CovariantVector<TParametersValueType, Self::InputSpaceDimension>;
  using OutputCovariantVectorType = CovariantVector<TParametersValueType, Self::OutputSpaceDimension>;
 
  using InputVnlVectorType = vnl_vector_fixed<TParametersValueType, Self::InputSpaceDimension>;
  using OutputVnlVectorType = vnl_vector_fixed<TParametersValueType, Self::OutputSpaceDimension>;
 
  using InputPointType = Point<TParametersValueType, Self::InputSpaceDimension>;
  using OutputPointType = Point<TParametersValueType, Self::OutputSpaceDimension>;
 
  using InverseTransformBaseType = typename Superclass::InverseTransformBaseType;
  using InverseTransformBasePointer = typename InverseTransformBaseType::Pointer;
 
  OutputPointType
  TransformPoint(const InputPointType & point) const override
  {
    return point;
  }
 
  using Superclass::TransformVector;
  OutputVectorType
  TransformVector(const InputVectorType & vector) const override
  {
    return vector;
  }
 
  OutputVnlVectorType
  TransformVector(const InputVnlVectorType & vector) const override
  {
    return vector;
  }
 
  using Superclass::TransformCovariantVector;
  OutputCovariantVectorType
  TransformCovariantVector(const InputCovariantVectorType & vector) const override
  {
    return vector;
  }
 
  void
  SetIdentity()
  {}
 
  void
  ComputeJacobianWithRespectToParameters(const InputPointType &, JacobianType & jacobian) const override
  {
    jacobian = this->m_ZeroJacobian;
  }
 
 
  void
  ComputeJacobianWithRespectToPosition(const InputPointType &, JacobianPositionType & jac) const override
  {
    jac.set_identity();
  }
  using Superclass::ComputeJacobianWithRespectToPosition;
 
  /* Always returns true if not null, as an identity is it's own inverse */
  bool
  GetInverse(Self * inverseTransform) const
  {
    return (inverseTransform != nullptr);
  }
 
  InverseTransformBasePointer
  GetInverseTransform() const override
  {
    return this->New().GetPointer();
  }
 
  TransformCategoryEnum
  GetTransformCategory() const override
  {
    return Self::TransformCategoryEnum::Linear;
  }
 
  const FixedParametersType &
  GetFixedParameters() const override
  {
    return this->m_FixedParameters;
  }
 
  void
  SetFixedParameters(const FixedParametersType &) override
  {}
 
  const ParametersType &
  GetParameters() const override
  {
    return this->m_Parameters;
  }
 
  void
  SetParameters(const ParametersType &) override
  {}
 
protected:
  IdentityTransform()
    : Transform<TParametersValueType, NDimensions, NDimensions>(0)
    , m_ZeroJacobian(NDimensions, 0)
  {
    // The Jacobian is constant, therefore it can be initialized in the
    // constructor.
    this->m_ZeroJacobian.Fill(0.0);
  }
 
  ~IdentityTransform() override = default;
 
private:
  JacobianType m_ZeroJacobian;
};
} // end namespace itk
 
#endif