irplib_fft.c

/*
 * This file is part of the IRPLIB Pipeline
 * Copyright (C) 2002,2003,2014 European Southern Observatory
 *
 * 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 St, Fifth Floor, Boston, MA  02111-1307  USA
 */
 
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
 
/*-----------------------------------------------------------------------------
                                   Includes
 -----------------------------------------------------------------------------*/
 
#include "irplib_fft.h"
 
/*----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------*/

 
 
/*----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------*/
cpl_error_code
irplib_image_find_shift(const cpl_image *self,
                        const cpl_image *other,
                        double *px,
                        double *py)
{
    const cpl_size nx = cpl_image_get_size_x(self);
    const cpl_size ny = cpl_image_get_size_y(self);
    const cpl_size type = cpl_image_get_type(self);
    const size_t bufsz =
        (size_t)(nx * ny) * cpl_type_get_sizeof(type | CPL_TYPE_COMPLEX);
    cpl_imagelist *iml;
    cpl_imagelist *fml;
    cpl_image *fself;
    cpl_image *fother;
    void *fdata;
    cpl_error_code code = CPL_ERROR_NONE;
 
    cpl_ensure_code(px != NULL, CPL_ERROR_NULL_INPUT);
    cpl_ensure_code(py != NULL, CPL_ERROR_NULL_INPUT);
 
    iml = cpl_imagelist_new();
    /* Input images _not_ modified */
    CPL_DIAG_PRAGMA_PUSH_IGN(-Wcast-qual);
    cpl_imagelist_set(iml, (cpl_image *)self, 0);
    cpl_imagelist_set(iml, (cpl_image *)other, 1);
    CPL_DIAG_PRAGMA_POP;
 
    fdata = cpl_calloc(2, bufsz); /* Don't need two calloc()s here */
 
    fml = cpl_imagelist_new();
    fself = cpl_image_wrap(nx, ny, type | CPL_TYPE_COMPLEX, fdata);
    fother =
        cpl_image_wrap(nx, ny, type | CPL_TYPE_COMPLEX, (char *)fdata + bufsz);
 
    cpl_imagelist_set(fml, fself, 0);
    cpl_imagelist_set(fml, fother, 1);
 
    if (cpl_fft_imagelist(fml, iml, CPL_FFT_FORWARD)) {
        code = cpl_error_set_where(cpl_func);
    }
    else {
        /* Should not be able to fail now */
        cpl_size xmax = 1, ymax = 1;
        /* Share pixel buffer with fself which is not needed at the same time */
        cpl_image *imgpos =
            cpl_image_wrap(nx, ny, type, cpl_image_get_data(fself));
 
        /* Cross-correlate */
        cpl_image_conjugate(fother, fother);
        cpl_image_multiply(fother, fself);
 
        cpl_fft_image(imgpos, fother, CPL_FFT_BACKWARD | CPL_FFT_NOSCALE);
 
        cpl_image_get_maxpos(imgpos, &xmax, &ymax);
 
        (void)cpl_image_unwrap(imgpos);
 
        /* The pixel position starts from 1, the offset from 0 */
        xmax--;
        ymax--;
 
        /* The offset is signed, from -N/2 to N/2-1 */
        *px = 2 * xmax >= nx ? xmax - nx : xmax;
        *py = 2 * ymax >= ny ? ymax - ny : ymax;
    }
 
    cpl_imagelist_unwrap(iml);
    cpl_image_unwrap(cpl_imagelist_unset(fml, 1));
    cpl_imagelist_delete(fml);
 
    return code;
}