1 /*=========================================================================
2  *
3  *  Copyright Insight Software Consortium
4  *
5  *  Licensed under the Apache License, Version 2.0 (the "License");
6  *  you may not use this file except in compliance with the License.
7  *  You may obtain a copy of the License at
8  *
9  *         http://www.apache.org/licenses/LICENSE-2.0.txt
10  *
11  *  Unless required by applicable law or agreed to in writing, software
12  *  distributed under the License is distributed on an "AS IS" BASIS,
13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  *  See the License for the specific language governing permissions and
15  *  limitations under the License.
16  *
17  *=========================================================================*/
18 #ifndef itkBSplineInterpolationWeightFunction_h
19 #define itkBSplineInterpolationWeightFunction_h
20 
21 #include "itkFunctionBase.h"
22 #include "itkContinuousIndex.h"
23 #include "itkBSplineKernelFunction.h"
24 #include "itkArray.h"
25 #include "itkArray2D.h"
26 
27 namespace itk
28 {
29 /** \class BSplineInterpolationWeightFunction
30  * \brief Returns the weights over the support region used for B-spline
31  * interpolation/reconstruction.
32  *
33  * Computes/evaluate the B-spline interpolation weights over the
34  * support region of the B-spline.
35  *
36  * This class is templated over the coordinate representation type,
37  * the space dimension and the spline order.
38  *
39  * \sa Point
40  * \sa Index
41  * \sa ContinuousIndex
42  *
43  * \ingroup Functions ImageInterpolators
44  * \ingroup ITKCommon
45  */
46 template<
47   typename TCoordRep = float,
48   unsigned int VSpaceDimension = 2,
49   unsigned int VSplineOrder = 3
50   >
51 class ITK_TEMPLATE_EXPORT BSplineInterpolationWeightFunction:
52   public FunctionBase< ContinuousIndex< TCoordRep, VSpaceDimension >,
53                        Array< double > >
54 {
55 public:
56   ITK_DISALLOW_COPY_AND_ASSIGN(BSplineInterpolationWeightFunction);
57 
58   /** Standard class type aliases. */
59   using Self = BSplineInterpolationWeightFunction;
60   using Superclass = FunctionBase< ContinuousIndex< TCoordRep, VSpaceDimension >,
61                         Array< double > >;
62 
63   using Pointer = SmartPointer< Self >;
64   using ConstPointer = SmartPointer< const Self >;
65 
66   /** New macro for creation of through the object factory. */
67   itkNewMacro(Self);
68 
69   /** Run-time type information (and related methods). */
70   itkTypeMacro(BSplineInterpolationWeightFunction, FunctionBase);
71 
72   /** Space dimension. */
73   static constexpr unsigned int SpaceDimension = VSpaceDimension;
74 
75   /** Spline order. */
76   static constexpr unsigned int SplineOrder = VSplineOrder;
77 
78   /** OutputType type alias support. */
79   using WeightsType = Array< double >;
80 
81   /** Index and size type alias support. */
82   using IndexType = Index< VSpaceDimension >;
83   using SizeType = Size< VSpaceDimension >;
84 
85   /** ContinuousIndex type alias support. */
86   using ContinuousIndexType = ContinuousIndex< TCoordRep, VSpaceDimension >;
87 
88   /** Evaluate the weights at specified ContinuousIndex position.
89    * Subclasses must provide this method. */
90   WeightsType Evaluate(const ContinuousIndexType & index) const override;
91 
92   /** Evaluate the weights at specified ContinuousIndex position.
93    * The weights are returned in the user specified container.
94    * This function assume that weights can hold
95    * (SplineOrder + 1)^(SpaceDimension) elements. For efficiency,
96    * no size checking is done.
97    * On return, startIndex contains the start index of the
98    * support region over which the weights are defined.
99    */
100   virtual void Evaluate(const ContinuousIndexType & index,
101                         WeightsType & weights, IndexType & startIndex) const;
102 
103   /** Get support region size. */
104   itkGetConstMacro(SupportSize, SizeType);
105 
106   /** Get number of weights. */
107   itkGetConstMacro(NumberOfWeights, unsigned int);
108 
109 protected:
110   BSplineInterpolationWeightFunction();
111   ~BSplineInterpolationWeightFunction() override = default;
112   void PrintSelf(std::ostream & os, Indent indent) const override;
113 
114 private:
115   /** Number of weights. */
116   unsigned int m_NumberOfWeights;
117 
118   /** Size of support region. */
119   SizeType m_SupportSize;
120 
121   /** Lookup table type. */
122   using TableType = Array2D< unsigned int >;
123 
124   /** Table mapping linear offset to indices. */
125   TableType m_OffsetToIndexTable;
126 
127   /** Interpolation kernel type. */
128   using KernelType = BSplineKernelFunction< Self::SplineOrder >;
129 
130   /** Interpolation kernel. */
131   typename KernelType::Pointer m_Kernel;
132 };
133 } // end namespace itk
134 
135 #ifndef ITK_MANUAL_INSTANTIATION
136 #include "itkBSplineInterpolationWeightFunction.hxx"
137 #endif
138 
139 #endif
140