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 itkDerivativeOperator_hxx
19 #define itkDerivativeOperator_hxx
20 #include "itkDerivativeOperator.h"
21
22 #include "itkNumericTraits.h"
23
24 namespace itk
25 {
26 template< typename TPixel, unsigned int VDimension, typename TAllocator >
27 typename DerivativeOperator< TPixel, VDimension, TAllocator >
28 ::CoefficientVector
29 DerivativeOperator< TPixel, VDimension, TAllocator >
GenerateCoefficients()30 ::GenerateCoefficients()
31 {
32 unsigned int i;
33 unsigned int j;
34 PixelRealType previous;
35 PixelRealType next;
36 const unsigned int w = 2 * ( ( m_Order + 1 ) / 2 ) + 1;
37 CoefficientVector coeff(w);
38
39 coeff[w / 2] = 1.0;
40 for ( i = 0; i < m_Order / 2; i++ )
41 {
42 previous = coeff[1] - 2 * coeff[0];
43 for ( j = 1; j < w - 1; j++ )
44 {
45 next = coeff[j - 1] + coeff[j + 1] - 2 * coeff[j];
46 coeff[j - 1] = previous;
47 previous = next;
48 }
49 next = coeff[j - 1] - 2 * coeff[j];
50 coeff[j - 1] = previous;
51 coeff[j] = next;
52 }
53 for ( i = 0; i < m_Order % 2; i++ )
54 {
55 previous = 0.5 * coeff[1];
56 for ( j = 1; j < w - 1; j++ )
57 {
58 next = -0.5 * coeff[j - 1] + 0.5 * coeff[j + 1];
59 coeff[j - 1] = previous;
60 previous = next;
61 }
62 next = -0.5 * coeff[j - 1];
63 coeff[j - 1] = previous;
64 coeff[j] = next;
65 }
66
67 return coeff;
68 }
69 } // namespace itk
70
71 #endif
72