/* Inverse FFT
 *
 * Author: Nicos Dessipris
 * Written on: 12/04/1990
 * Modified on :
 * 28/6/95 JC
 *	- rewritten, based on new im_invfft() code
 * 10/9/98 JC
 *	- frees memory more quickly
 * 2/4/02 JC
 *	- fftw code added
 * 13/7/02 JC
 *	- Type reset
 * 27/2/03 JC
 *	- tiny speed-up ... save 1 copy on write
 * 22/1/04 JC
 *	- oops, fix for segv on wider than high fftw transforms
 * 3/11/04
 *	- added fftw3 support
 * 7/2/10
 * 	- gtkdoc
 * 27/1/12
 * 	- better setting of interpretation
 * 	- remove own fft fallback code
 * 	- remove fftw2 path
 * 	- reduce memuse
 * 3/1/14
 * 	- redone as a class
 */

/*

	This file is part of VIPS.

	VIPS is free software; you can redistribute it and/or modify
	it under the terms of the GNU Lesser 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 Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser 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

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>
#include <stdlib.h>

#include <vips/vips.h>
#include <vips/internal.h>
#include "pfreqfilt.h"

#ifdef HAVE_FFTW

#include <fftw3.h>

typedef struct _VipsInvfft {
	VipsFreqfilt parent_instance;

	gboolean real;

} VipsInvfft;

typedef VipsFreqfiltClass VipsInvfftClass;

G_DEFINE_TYPE(VipsInvfft, vips_invfft, VIPS_TYPE_FREQFILT);

/* Complex to complex inverse transform.
 */
static int
cinvfft1(VipsObject *object, VipsImage *in, VipsImage **out)
{
	VipsImage **t = (VipsImage **) vips_object_local_array(object, 4);
	VipsInvfft *invfft = (VipsInvfft *) object;
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS(invfft);

	fftw_plan plan;
	double *planner_scratch;

	if (vips_check_mono(class->nickname, in) ||
		vips_check_uncoded(class->nickname, in))
		return -1;

	/* Convert input to a complex double membuffer.
	 */
	*out = vips_image_new_memory();
	if (vips_cast_dpcomplex(in, &t[0], NULL) ||
		vips_image_write(t[0], *out))
		return -1;

	/* Make the plan for the transform. Yes, they really do use nx for
	 * height and ny for width.
	 */
	if (!(planner_scratch = VIPS_ARRAY(invfft,
			  VIPS_IMAGE_N_PELS(in) * 2, double)))
		return -1;
	if (!(plan = fftw_plan_dft_2d(in->Ysize, in->Xsize,
			  (fftw_complex *) planner_scratch,
			  (fftw_complex *) planner_scratch,
			  FFTW_BACKWARD,
			  0))) {
		vips_error(class->nickname,
			"%s", _("unable to create transform plan"));
		return -1;
	}

	fftw_execute_dft(plan,
		(fftw_complex *) (*out)->data, (fftw_complex *) (*out)->data);

	fftw_destroy_plan(plan);

	(*out)->Type = VIPS_INTERPRETATION_B_W;

	return 0;
}

/* Complex to real inverse transform.
 */
static int
rinvfft1(VipsObject *object, VipsImage *in, VipsImage **out)
{
	VipsImage **t = (VipsImage **) vips_object_local_array(object, 4);
	VipsInvfft *invfft = (VipsInvfft *) object;
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS(invfft);
	const int half_width = in->Xsize / 2 + 1;

	double *half_complex;
	double *planner_scratch;
	fftw_plan plan;
	int x, y;
	double *q, *p;

	/* Convert input to a complex double membuffer.
	 */
	t[1] = vips_image_new_memory();
	if (vips_cast_dpcomplex(in, &t[0], NULL) ||
		vips_image_write(t[0], t[1]))
		return -1;

	/* Build half-complex image.
	 */
	if (!(half_complex = VIPS_ARRAY(invfft,
			  t[1]->Ysize * half_width * 2, double)))
		return -1;
	q = half_complex;
	for (y = 0; y < t[1]->Ysize; y++) {
		p = ((double *) t[1]->data) + (guint64) y * t[1]->Xsize * 2;

		for (x = 0; x < half_width; x++) {
			q[0] = p[0];
			q[1] = p[1];
			p += 2;
			q += 2;
		}
	}

	/* Make mem buffer real image for output.
	 */
	*out = vips_image_new_memory();
	if (vips_image_pipelinev(*out, VIPS_DEMAND_STYLE_ANY, t[1], NULL))
		return -1;
	(*out)->BandFmt = VIPS_FORMAT_DOUBLE;
	(*out)->Type = VIPS_INTERPRETATION_B_W;
	if (vips_image_write_prepare(*out))
		return -1;

	/* Make the plan for the transform. Yes, they really do use nx for
	 * height and ny for width.
	 */
	if (!(planner_scratch = VIPS_ARRAY(invfft,
			  t[1]->Ysize * half_width * 2, double)))
		return -1;
	if (!(plan = fftw_plan_dft_c2r_2d(t[1]->Ysize, t[1]->Xsize,
			  (fftw_complex *) planner_scratch, (double *) (*out)->data,
			  0))) {
		vips_error(class->nickname,
			"%s", _("unable to create transform plan"));
		return -1;
	}

	fftw_execute_dft_c2r(plan,
		(fftw_complex *) half_complex, (double *) (*out)->data);

	fftw_destroy_plan(plan);

	return 0;
}

static int
vips_invfft_build(VipsObject *object)
{
	VipsFreqfilt *freqfilt = VIPS_FREQFILT(object);
	VipsInvfft *invfft = (VipsInvfft *) object;
	VipsImage **t = (VipsImage **) vips_object_local_array(object, 4);

	VipsImage *in;

	if (VIPS_OBJECT_CLASS(vips_invfft_parent_class)->build(object))
		return -1;

	in = freqfilt->in;

	if (vips_image_decode(in, &t[0]))
		return -1;
	in = t[0];

	if (invfft->real) {
		if (vips__fftproc(VIPS_OBJECT(invfft),
				in, &t[1], rinvfft1))
			return -1;
	}
	else {
		if (vips__fftproc(VIPS_OBJECT(invfft),
				in, &t[1], cinvfft1))
			return -1;
	}

	if (vips_image_write(t[1], freqfilt->out))
		return -1;

	return 0;
}

static void
vips_invfft_class_init(VipsInvfftClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "invfft";
	vobject_class->description = _("inverse FFT");
	vobject_class->build = vips_invfft_build;

	VIPS_ARG_BOOL(class, "real", 4,
		_("Real"),
		_("Output only the real part of the transform"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsInvfft, real),
		FALSE);
}

static void
vips_invfft_init(VipsInvfft *invfft)
{
}

#endif /*HAVE_FFTW*/

/**
 * vips_invfft: (method)
 * @in: input image
 * @out: (out): output image
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @real: only output the real part
 *
 * Transform an image from Fourier space to real space. The result is complex.
 * If you are OK with a real result, set @real, it's quicker.
 *
 * VIPS uses the fftw Fourier Transform library. If this library was not
 * available when VIPS was configured, these functions will fail.
 *
 * See also: vips_fwfft().
 *
 * Returns: 0 on success, -1 on error.
 */
int
vips_invfft(VipsImage *in, VipsImage **out, ...)
{
	va_list ap;
	int result;

	va_start(ap, out);
	result = vips_call_split("invfft", ap, in, out);
	va_end(ap);

	return result;
}
