/* creates an butterworth filter.
 *
 * 02/01/14
 * 	- from butterworth.c
 */

/*

	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

 */

/*
#define VIPS_DEBUG
 */

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

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

#include <vips/vips.h>

#include "pcreate.h"
#include "point.h"
#include "pmask.h"

typedef struct _VipsMaskButterworthRing {
	VipsMaskButterworth parent_instance;

	double ringwidth;

} VipsMaskButterworthRing;

typedef VipsMaskButterworthClass VipsMaskButterworthRingClass;

G_DEFINE_TYPE(VipsMaskButterworthRing, vips_mask_butterworth_ring,
	VIPS_TYPE_MASK_BUTTERWORTH);

static double
vips_mask_butterworth_ring_point(VipsMask *mask,
	double dx, double dy)
{
	VipsMaskButterworth *butterworth =
		(VipsMaskButterworth *) mask;
	VipsMaskButterworthRing *butterworth_ring =
		(VipsMaskButterworthRing *) mask;

	double order = butterworth->order;
	double fc = butterworth->frequency_cutoff;
	double ac = butterworth->amplitude_cutoff;
	double ringwidth = butterworth_ring->ringwidth;

	double df = ringwidth / 2.0;
	double cnst = (1.0 / ac) - 1.0;
	double df2 = df * df;
	double dist = sqrt(dx * dx + dy * dy);

	return 1.0 /
		(1.0 + cnst * pow((dist - fc) * (dist - fc) / df2, order));
}

static void
vips_mask_butterworth_ring_class_init(
	VipsMaskButterworthRingClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);
	VipsMaskClass *mask_class = VIPS_MASK_CLASS(class);

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

	vobject_class->nickname = "mask_butterworth_ring";
	vobject_class->description = _("make a butterworth ring filter");

	mask_class->point = vips_mask_butterworth_ring_point;

	VIPS_ARG_DOUBLE(class, "ringwidth", 20,
		_("Ringwidth"),
		_("Ringwidth"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsMaskButterworthRing, ringwidth),
		0.0, 1000000.0, 0.1);
}

static void
vips_mask_butterworth_ring_init(
	VipsMaskButterworthRing *butterworth_ring)
{
	butterworth_ring->ringwidth = 0.1;
}

/**
 * vips_mask_butterworth_ring:
 * @out: (out): output image
 * @width: image size
 * @height: image size
 * @order: filter order
 * @frequency_cutoff: frequency threshold
 * @amplitude_cutoff: amplitude threshold
 * @ringwidth: ringwidth
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @nodc: don't set the DC pixel
 * * @reject: invert the filter sense
 * * @optical: coordinates in optical space
 * * @uchar: output a uchar image
 *
 * Make a butterworth ring-pass or ring-reject filter, that is, one with a
 * variable,
 * smooth transition
 * positioned at @frequency_cutoff of width @width, where @frequency_cutoff is
 * in the range 0 - 1. The shape of the curve is controlled by
 * @order --- higher values give a sharper transition. See Gonzalez and Wintz,
 * Digital Image Processing, 1987.
 *
 * See also: vips_mask_ideal().
 *
 * Returns: 0 on success, -1 on error
 */
int
vips_mask_butterworth_ring(VipsImage **out, int width, int height,
	double order, double frequency_cutoff, double amplitude_cutoff,
	double ringwidth, ...)
{
	va_list ap;
	int result;

	va_start(ap, ringwidth);
	result = vips_call_split("mask_butterworth_ring", ap,
		out, width, height,
		order, frequency_cutoff, amplitude_cutoff, ringwidth);
	va_end(ap);

	return result;
}
