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/*=========================================================================
*
* Copyright UMC Utrecht and contributors
*
* 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 itkBSplineInterpolationWeightFunctionBase_h
#define itkBSplineInterpolationWeightFunctionBase_h
#include "itkFunctionBase.h"
#include "itkContinuousIndex.h"
#include "itkIndexRange.h"
#include "itkMath.h"
#include "itkMatrix.h"
#include "itkBSplineKernelFunction2.h"
#include "itkBSplineDerivativeKernelFunction.h"
#include "itkBSplineSecondOrderDerivativeKernelFunction2.h"
namespace itk
{
/** \class BSplineInterpolationWeightFunctionBase
* \brief Returns the weights over the support region used for B-spline
* interpolation/reconstruction.
*
* Computes/evaluate the B-spline interpolation weights over the
* support region of the B-spline.
*
* This class is templated over the coordinate representation type,
* the space dimension and the spline order.
*
* \sa Point
* \sa Index
* \sa ContinuousIndex
*
* \ingroup Functions ImageInterpolators
*/
template <typename TCoordinate = float, unsigned int VSpaceDimension = 2, unsigned int VSplineOrder = 3>
class ITK_TEMPLATE_EXPORT BSplineInterpolationWeightFunctionBase
: public FunctionBase<ContinuousIndex<TCoordinate, VSpaceDimension>,
FixedArray<double, Math::UnsignedPower(VSplineOrder + 1, VSpaceDimension)>>
{
public:
ITK_DISALLOW_COPY_AND_MOVE(BSplineInterpolationWeightFunctionBase);
/** Standard class typedefs. */
using Self = BSplineInterpolationWeightFunctionBase;
using Superclass = FunctionBase<ContinuousIndex<TCoordinate, VSpaceDimension>,
FixedArray<double, Math::UnsignedPower(VSplineOrder + 1, VSpaceDimension)>>;
using Pointer = SmartPointer<Self>;
using ConstPointer = SmartPointer<const Self>;
/** Run-time type information (and related methods). */
itkOverrideGetNameOfClassMacro(BSplineInterpolationWeightFunctionBase);
/** Space dimension. */
itkStaticConstMacro(SpaceDimension, unsigned int, VSpaceDimension);
/** Spline order. */
itkStaticConstMacro(SplineOrder, unsigned int, VSplineOrder);
/** The number of weights as a static const. */
static constexpr unsigned long NumberOfWeights = Math::UnsignedPower(VSplineOrder + 1, VSpaceDimension);
/** OutputType typedef support. */
using WeightsType = FixedArray<double, NumberOfWeights>;
/** Index and size typedef support. */
using IndexType = Index<VSpaceDimension>;
using SizeType = Size<VSpaceDimension>;
/** ContinuousIndex typedef support. */
using ContinuousIndexType = ContinuousIndex<TCoordinate, VSpaceDimension>;
/** Evaluate the weights at specified ContinousIndex position. */
WeightsType
Evaluate(const ContinuousIndexType & index) const override;
/** Evaluate the weights at specified ContinousIndex position.
* The weights are returned in the user specified container.
* On return, startIndex contains the start index of the
* support region over which the weights are defined.
*/
WeightsType
Evaluate(const ContinuousIndexType & cindex, const IndexType & startIndex) const;
/** Compute the start index of the support region. */
static IndexType
ComputeStartIndex(const ContinuousIndexType & index);
/** The support region size: a hypercube of length SplineOrder + 1 */
static constexpr SizeType SupportSize{ SizeType::Filled(VSplineOrder + 1) };
protected:
BSplineInterpolationWeightFunctionBase() = default;
~BSplineInterpolationWeightFunctionBase() override = default;
/** Interpolation kernel types. */
using KernelType = BSplineKernelFunction2<VSplineOrder>;
using KernelPointer = typename KernelType::Pointer;
using DerivativeKernelType = BSplineDerivativeKernelFunction<VSplineOrder>;
using DerivativeKernelPointer = typename DerivativeKernelType::Pointer;
using SecondOrderDerivativeKernelType = BSplineSecondOrderDerivativeKernelFunction2<VSplineOrder>;
using SecondOrderDerivativeKernelPointer = typename SecondOrderDerivativeKernelType::Pointer;
using WeightArrayType = typename KernelType::WeightArrayType;
/** Typedef for intermediary 1D weights.
* The Matrix is at least twice as fast as std::vector< vnl_vector< double > >,
* probably because of the fixed size at compile time.
*/
using OneDWeightsType = Matrix<double, Self::SpaceDimension, VSplineOrder + 1>;
/** Compute the 1D weights. */
virtual void
Compute1DWeights(const ContinuousIndexType & index,
const IndexType & startIndex,
OneDWeightsType & weights1D) const = 0;
/** Print the member variables. */
void
PrintSelf(std::ostream & os, Indent indent) const override;
private:
/** Lookup table type. */
using TableType = FixedArray<IndexType, NumberOfWeights>;
/** Table mapping linear offset to indices. */
const TableType m_OffsetToIndexTable{ [] {
TableType table;
std::copy_n(ZeroBasedIndexRange<SpaceDimension>(SupportSize).cbegin(), NumberOfWeights, table.begin());
return table;
}() };
};
} // end namespace itk
#ifndef ITK_MANUAL_INSTANTIATION
# include "itkBSplineInterpolationWeightFunctionBase.hxx"
#endif
#endif
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