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/**
* \file fft.c
*
* \brief Fast Fourier Transformation of Two Dimensional Satellite Data
* functions.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* \author GRASS GIS Development Team
*
* \date 2001-2006
*/
#include <grass/config.h>
#if defined(HAVE_FFTW3_H) || defined(HAVE_FFTW_H) || defined(HAVE_DFFTW_H)
#if defined(HAVE_FFTW3_H)
#include <fftw3.h>
#define c_re(c) ((c)[0])
#define c_im(c) ((c)[1])
#elif defined(HAVE_FFTW_H)
#include <fftw.h>
#elif defined(HAVE_DFFTW_H)
#include <dfftw.h>
#endif
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <grass/gmath.h>
#include <grass/gis.h>
/**
* \fn int fft2(int i_sign, double (*data)[2], int NN, int dimc, int dimr)
*
* \brief Fast Fourier Transform for two-dimensional array.
*
* Fast Fourier Transform for two-dimensional array.<br>
* <bNote:</b> If passing real data to fft() forward transform
* (especially when using fft() in a loop), explicitly (re-)initialize
* the imaginary part to zero (DATA[1][i] = 0.0). Returns 0.
*
* \param[in] i_sign Direction of transform -1 is normal, +1 is inverse
* \param[in,out] data Pointer to complex linear array in row major order
* containing data and result
* \param[in] NN Value of DATA dimension (dimc * dimr)
* \param[in] dimc Value of image column dimension (max power of 2)
* \param[in] dimr Value of image row dimension (max power of 2)
* \return int always returns 0
*/
int fft2(int i_sign, double (*data)[2], int NN, int dimc, int dimr)
{
#ifdef HAVE_FFTW3_H
fftw_plan plan;
#else
fftwnd_plan plan;
#endif
double norm;
int i;
norm = 1.0 / sqrt(NN);
#ifdef HAVE_FFTW3_H
plan = fftw_plan_dft_2d(dimr, dimc, data, data,
(i_sign < 0) ? FFTW_FORWARD : FFTW_BACKWARD,
FFTW_ESTIMATE);
fftw_execute(plan);
fftw_destroy_plan(plan);
#else
plan = fftw2d_create_plan(dimc, dimr,
(i_sign < 0) ? FFTW_FORWARD : FFTW_BACKWARD,
FFTW_ESTIMATE | FFTW_IN_PLACE);
fftwnd_one(plan, data, data);
fftwnd_destroy_plan(plan);
#endif
for (i = 0; i < NN; i++) {
data[i][0] *= norm;
data[i][1] *= norm;
}
return 0;
}
/**
* \fn int fft(int i_sign, double *DATA[2], int NN, int dimc, int dimr)
*
* \brief Fast Fourier Transform for two-dimensional array.
*
* Fast Fourier Transform for two-dimensional array.<br>
* <bNote:</b> If passing real data to fft() forward transform
* (especially when using fft() in a loop), explicitly (re-)initialize
* the imaginary part to zero (DATA[1][i] = 0.0). Returns 0.
*
* \param[in] i_sign Direction of transform -1 is normal, +1 is inverse
* \param[in,out] DATA Pointer to complex linear array in row major order
* containing data and result
* \param[in] NN Value of DATA dimension (dimc * dimr)
* \param[in] dimc Value of image column dimension (max power of 2)
* \param[in] dimr Value of image row dimension (max power of 2)
* \return int always returns 0
*/
int fft(int i_sign, double *DATA[2], int NN, int dimc, int dimr)
{
fftw_complex *data;
int i;
data = (fftw_complex *)G_malloc(NN * sizeof(fftw_complex));
for (i = 0; i < NN; i++) {
c_re(data[i]) = DATA[0][i];
c_im(data[i]) = DATA[1][i];
}
fft2(i_sign, data, NN, dimc, dimr);
for (i = 0; i < NN; i++) {
DATA[0][i] = c_re(data[i]);
DATA[1][i] = c_im(data[i]);
}
G_free(data);
return 0;
}
#endif /* HAVE_FFT */
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