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 itkForwardDifferenceOperator_h
19 #define itkForwardDifferenceOperator_h
20 
21 #include "itkNeighborhoodOperator.h"
22 
23 namespace itk
24 {
25 /**
26  * \class ForwardDifferenceOperator
27  * \brief Operator whose inner product with a neighborhood returns
28  * a "half" derivative at the center of the neighborhood.
29  *
30  * ForwardDifferenceOperator uses forward differences
31  * i.e. F(x+1) - F(x) to calculate a "half" derivative useful, among
32  * other things, in solving differential equations. It is a directional
33  * NeighborhoodOperator that should be applied to a Neighborhood using the
34  * inner product.
35  *
36  * \ingroup Operators
37  * \ingroup ITKCommon
38  *
39  * \wiki
40  * \wikiexample{Operators/ForwardDifferenceOperator,Create a forward difference kernel}
41  * \endwiki
42  */
43 template< typename TPixel, unsigned int VDimension = 2,
44           typename TAllocator = NeighborhoodAllocator< TPixel > >
45 class ITK_TEMPLATE_EXPORT ForwardDifferenceOperator:
46   public NeighborhoodOperator< TPixel, VDimension, TAllocator >
47 {
48 public:
49   /** Standard class type aliases. */
50   using Self = ForwardDifferenceOperator;
51   using Superclass = NeighborhoodOperator< TPixel, VDimension, TAllocator >;
52 
53   using PixelType = typename Superclass::PixelType;
54 
55   /** Constructor. */
56   ForwardDifferenceOperator() = default;
57 
58   /** Copy constructor */
ForwardDifferenceOperator(const Self & other)59   ForwardDifferenceOperator(const Self & other):
60     NeighborhoodOperator< TPixel, VDimension, TAllocator >(other) {}
61 
62   /** Assignment operator */
63   Self & operator=(const Self & other)
64   {
65     Superclass::operator=(other);
66     return *this;
67   }
68 
69 protected:
70   /** Necessary to work around VC++ compiler bug. */
71   using CoefficientVector = typename Superclass::CoefficientVector;
72 
73   /** Calculates operator coefficients. */
74   CoefficientVector GenerateCoefficients() override;
75 
76   /** Arranges coefficients spatially in the memory buffer. */
Fill(const CoefficientVector & coeff)77   void Fill(const CoefficientVector & coeff) override
78   {
79     this->FillCenteredDirectional(coeff);
80   }
81 };
82 } // namespace itk
83 
84 #ifndef ITK_MANUAL_INSTANTIATION
85 #include "itkForwardDifferenceOperator.hxx"
86 #endif
87 
88 #endif
89