GRASS GIS 8 Programmer's Manual 8.2.0(2022)-exported
fft.c
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1
2/**
3 * \file fft.c
4 *
5 * \brief Fast Fourier Transformation of Two Dimensional Satellite Data functions.
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or (at
10 * your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful, but
13 * WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 *
21 * \author GRASS GIS Development Team
22 *
23 * \date 2001-2006
24 */
25
26#include <grass/config.h>
27
28#if defined(HAVE_FFTW_H) || defined(HAVE_DFFTW_H) || defined(HAVE_FFTW3_H)
29
30#ifdef HAVE_FFTW_H
31#include <fftw.h>
32#endif
33
34#ifdef HAVE_DFFTW_H
35#include <dfftw.h>
36#endif
37
38#ifdef HAVE_FFTW3_H
39#include <fftw3.h>
40#define c_re(c) ((c)[0])
41#define c_im(c) ((c)[1])
42#endif
43
44#include <stdlib.h>
45#include <stdio.h>
46#include <math.h>
47#include <grass/gmath.h>
48#include <grass/gis.h>
49
50
51/**
52 * \fn int fft2(int i_sign, double (*data)[2], int NN, int dimc, int dimr)
53 *
54 * \brief Fast Fourier Transform for two-dimensional array.
55 *
56 * Fast Fourier Transform for two-dimensional array.<br>
57 * <bNote:</b> If passing real data to fft() forward transform
58 * (especially when using fft() in a loop), explicitly (re-)initialize
59 * the imaginary part to zero (DATA[1][i] = 0.0). Returns 0.
60 *
61 * \param[in] i_sign Direction of transform -1 is normal, +1 is inverse
62 * \param[in,out] data Pointer to complex linear array in row major order
63 * containing data and result
64 * \param[in] NN Value of DATA dimension (dimc * dimr)
65 * \param[in] dimc Value of image column dimension (max power of 2)
66 * \param[in] dimr Value of image row dimension (max power of 2)
67 * \return int always returns 0
68 */
69
70int fft2(int i_sign, double (*data)[2], int NN, int dimc, int dimr)
71{
72#ifdef HAVE_FFTW3_H
73 fftw_plan plan;
74#else
75 fftwnd_plan plan;
76#endif
77 double norm;
78 int i;
79
80 norm = 1.0 / sqrt(NN);
81
82#ifdef HAVE_FFTW3_H
83 plan = fftw_plan_dft_2d(dimr, dimc, data, data,
84 (i_sign < 0) ? FFTW_FORWARD : FFTW_BACKWARD,
85 FFTW_ESTIMATE);
86
87 fftw_execute(plan);
88
89 fftw_destroy_plan(plan);
90#else
91 plan = fftw2d_create_plan(dimc, dimr,
92 (i_sign < 0) ? FFTW_FORWARD : FFTW_BACKWARD,
93 FFTW_ESTIMATE | FFTW_IN_PLACE);
94
95 fftwnd_one(plan, data, data);
96
97 fftwnd_destroy_plan(plan);
98#endif
99
100 for (i = 0; i < NN; i++) {
101 data[i][0] *= norm;
102 data[i][1] *= norm;
103 }
104
105 return 0;
106}
107
108/**
109 * \fn int fft(int i_sign, double *DATA[2], int NN, int dimc, int dimr)
110 *
111 * \brief Fast Fourier Transform for two-dimensional array.
112 *
113 * Fast Fourier Transform for two-dimensional array.<br>
114 * <bNote:</b> If passing real data to fft() forward transform
115 * (especially when using fft() in a loop), explicitly (re-)initialize
116 * the imaginary part to zero (DATA[1][i] = 0.0). Returns 0.
117 *
118 * \param[in] i_sign Direction of transform -1 is normal, +1 is inverse
119 * \param[in,out] DATA Pointer to complex linear array in row major order
120 * containing data and result
121 * \param[in] NN Value of DATA dimension (dimc * dimr)
122 * \param[in] dimc Value of image column dimension (max power of 2)
123 * \param[in] dimr Value of image row dimension (max power of 2)
124 * \return int always returns 0
125 */
126
127int fft(int i_sign, double *DATA[2], int NN, int dimc, int dimr)
128{
129 fftw_complex *data;
130 int i;
131
132 data = (fftw_complex *) G_malloc(NN * sizeof(fftw_complex));
133
134 for (i = 0; i < NN; i++) {
135 c_re(data[i]) = DATA[0][i];
136 c_im(data[i]) = DATA[1][i];
137 }
138
139 fft2(i_sign, data, NN, dimc, dimr);
140
141 for (i = 0; i < NN; i++) {
142 DATA[0][i] = c_re(data[i]);
143 DATA[1][i] = c_im(data[i]);
144 }
145
146 G_free(data);
147
148 return 0;
149}
150
151#endif /* HAVE_FFT */
void G_free(void *buf)
Free allocated memory.
Definition: alloc.c:149