ITK  6.0.0
Insight Toolkit
itkBSplineKernelFunction.h
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1/*=========================================================================
2 *
3 * Copyright NumFOCUS
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 * https://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 itkBSplineKernelFunction_h
19#define itkBSplineKernelFunction_h
20
22#include "itkMath.h"
23
24namespace itk
25{
42template <unsigned int VSplineOrder = 3, typename TRealValueType = double>
43class ITK_TEMPLATE_EXPORT BSplineKernelFunction : public KernelFunctionBase<TRealValueType>
44{
45public:
46 ITK_DISALLOW_COPY_AND_MOVE(BSplineKernelFunction);
47
52
53 using typename Superclass::RealType;
55 itkNewMacro(Self);
56
58 itkOverrideGetNameOfClassMacro(BSplineKernelFunction);
59
61 static constexpr unsigned int SplineOrder = VSplineOrder;
62
65 static TRealValueType
66 FastEvaluate(const TRealValueType u)
67 {
68 return Self::Evaluate(Dispatch<VSplineOrder>(), u);
69 }
70
72 TRealValueType
73 Evaluate(const TRealValueType & u) const override
74 {
75 return Self::FastEvaluate(u);
76 }
77
78protected:
80 ~BSplineKernelFunction() override = default;
81 void
82 PrintSelf(std::ostream & os, Indent indent) const override
83 {
84 Superclass::PrintSelf(os, indent);
85
86 os << indent << "SplineOrder: " << SplineOrder << std::endl;
87 }
88
89private:
92 {};
93 template <unsigned int>
94 struct Dispatch : public DispatchBase
95 {};
96
98 inline static TRealValueType
99 Evaluate(const Dispatch<0> &, const TRealValueType & u)
100 {
101 const TRealValueType absValue = itk::Math::abs(u);
102 if (absValue < TRealValueType{ 0.5 })
103 {
104 return TRealValueType{ 1.0 };
105 }
106 else if (Math::ExactlyEquals(absValue, TRealValueType{ 0.5 }))
107 {
108 return TRealValueType{ 0.5 };
109 }
110 else
111 {
112 return TRealValueType{ 0.0 };
113 }
114 }
118 inline static TRealValueType
119 Evaluate(const Dispatch<1> &, const TRealValueType & u)
120 {
121 const TRealValueType absValue = itk::Math::abs(u);
122 if (absValue < TRealValueType{ 1.0 })
123 {
124 return TRealValueType{ 1.0 } - absValue;
125 }
126 else
127 {
128 return TRealValueType{ 0.0 };
129 }
130 }
134 inline static TRealValueType
135 Evaluate(const Dispatch<2> &, const TRealValueType & u)
136 {
137 const TRealValueType absValue = itk::Math::abs(u);
138 if (absValue < TRealValueType{ 0.5 })
139 {
140 const TRealValueType sqrValue = itk::Math::sqr(absValue);
141 return TRealValueType{ 0.75 } - sqrValue;
142 }
143 else if (absValue < TRealValueType{ 1.5 })
144 {
145 const TRealValueType sqrValue = itk::Math::sqr(absValue);
146 // NOTE: 1.0/8.0 == 0.125
147 return (TRealValueType{ 9.0 } - TRealValueType{ 12.0 } * absValue + TRealValueType{ 4.0 } * sqrValue) *
148 TRealValueType{ 0.125 };
149 }
150 else
151 {
152 return TRealValueType{ 0.0 };
153 }
154 }
158 inline static TRealValueType
159 Evaluate(const Dispatch<3> &, const TRealValueType & u)
160 {
161 const TRealValueType absValue = itk::Math::abs(u);
162 if (absValue < TRealValueType{ 1.0 })
163 {
164 const TRealValueType sqrValue = itk::Math::sqr(absValue);
165 return (TRealValueType{ 4.0 } - TRealValueType{ 6.0 } * sqrValue + TRealValueType{ 3.0 } * sqrValue * absValue) /
166 TRealValueType{ 6.0 };
167 }
168 else if (absValue < TRealValueType{ 2.0 })
169 {
170 const TRealValueType sqrValue = itk::Math::sqr(absValue);
171 return (TRealValueType{ 8.0 } - TRealValueType{ 12.0 } * absValue + TRealValueType{ 6.0 } * sqrValue -
172 sqrValue * absValue) /
173 TRealValueType{ 6.0 };
174 }
175 else
176 {
177 return TRealValueType{ 0.0 };
178 }
179 }
183 inline static TRealValueType
184 Evaluate(const DispatchBase &, const TRealValueType &)
185 {
186 itkGenericExceptionMacro("Evaluate not implemented for spline order " << SplineOrder);
187 }
188};
189} // end namespace itk
192#endif
BSpline kernel used for density estimation and nonparametric regression.
static TRealValueType FastEvaluate(const TRealValueType u)
TRealValueType Evaluate(const TRealValueType &u) const override
~BSplineKernelFunction() override=default
static TRealValueType Evaluate(const Dispatch< 1 > &, const TRealValueType &u)
static TRealValueType Evaluate(const Dispatch< 3 > &, const TRealValueType &u)
static TRealValueType Evaluate(const DispatchBase &, const TRealValueType &)
static TRealValueType Evaluate(const Dispatch< 2 > &, const TRealValueType &u)
void PrintSelf(std::ostream &os, Indent indent) const override
static TRealValueType Evaluate(const Dispatch< 0 > &, const TRealValueType &u)
Control indentation during Print() invocation.
Definition: itkIndent.h:50
Kernel used for density estimation and nonparametric regression.
bool ExactlyEquals(const TInput1 &x1, const TInput2 &x2)
Return the result of an exact comparison between two scalar values of potentially different types.
Definition: itkMath.h:722
bool abs(bool x)
Definition: itkMath.h:840
The "itk" namespace contains all Insight Segmentation and Registration Toolkit (ITK) classes....