/* Match two normalised, cumulative histograms.
 *
 * Copyright: 1991, N. Dessipris.
 *
 * Author: Nicos Dessipris
 * Written on: 19/07/1990
 * Modified on: 26/03/1991
 *
 * 1/3/01 JC
 * 	- bleurg! rewritten, now does 16 bits as well, bugs removed, faster,
 *     	  smaller
 * 24/3/10
 * 	- gtkdoc
 * 	- small cleanups
 * 12/8/13
 * 	- redone im_histspec() as a class, vips_hist_match()
 * 19/12/13
 * 	- oop, upcast input
 */

/*

	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 <assert.h>

#include <vips/vips.h>

#include "phistogram.h"

/*
#define DEBUG
 */

typedef struct _VipsHistMatch {
	VipsHistogram parent_instance;

	VipsImage *in;
	VipsImage *ref;

} VipsHistMatch;

typedef VipsHistogramClass VipsHistMatchClass;

G_DEFINE_TYPE(VipsHistMatch, vips_hist_match, VIPS_TYPE_HISTOGRAM);

static void
vips_hist_match_process(VipsHistogram *histogram,
	VipsPel *out, VipsPel **in, int width)
{
	VipsHistMatch *match = (VipsHistMatch *) histogram;
	const int bands = match->in->Bands;
	const int max = width * bands;

	unsigned int *inbuf = (unsigned int *) in[0];
	unsigned int *refbuf = (unsigned int *) in[1];
	unsigned int *outbuf = (unsigned int *) out;

	int i, j;

	for (j = 0; j < bands; j++) {
		/* Track up refbuf[] with this.
		 */
		int ri = j;
		int limit = max - bands;

		for (i = j; i < max; i += bands) {
			unsigned int inv = inbuf[i];

			for (; ri < limit; ri += bands)
				if (inv <= refbuf[ri])
					break;

			if (ri < limit) {
				/* Simple rounding.
				 */
				double mid = refbuf[ri] +
					refbuf[ri + bands] / 2.0;

				if (inv < mid)
					outbuf[i] = ri / bands;
				else
					outbuf[i] = ri / bands + 1;
			}
			else
				outbuf[i] = refbuf[ri];
		}
	}
}

static int
vips_hist_match_build(VipsObject *object)
{
	VipsHistogram *histogram = VIPS_HISTOGRAM(object);
	VipsHistMatch *match = (VipsHistMatch *) object;

	histogram->n = 2;
	histogram->in = (VipsImage **) vips_object_local_array(object, 2);
	histogram->in[0] = match->in;
	histogram->in[1] = match->ref;

	if (histogram->in[0])
		g_object_ref(histogram->in[0]);
	if (histogram->in[1])
		g_object_ref(histogram->in[1]);

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

	return 0;
}

static void
vips_hist_match_class_init(VipsHistMatchClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);
	VipsHistogramClass *hclass = VIPS_HISTOGRAM_CLASS(class);

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

	vobject_class->nickname = "hist_match";
	vobject_class->description = _("match two histograms");
	vobject_class->build = vips_hist_match_build;

	hclass->input_format = VIPS_FORMAT_UINT;
	hclass->process = vips_hist_match_process;

	VIPS_ARG_IMAGE(class, "in", 1,
		_("Input"),
		_("Input histogram"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsHistMatch, in));

	VIPS_ARG_IMAGE(class, "ref", 2,
		_("Reference"),
		_("Reference histogram"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsHistMatch, ref));
}

static void
vips_hist_match_init(VipsHistMatch *match)
{
}

/**
 * vips_hist_match: (method)
 * @in: input histogram
 * @ref: reference histogram
 * @out: (out): output histogram
 * @...: %NULL-terminated list of optional named arguments
 *
 * Adjust @in to match @ref. If @in and @ref are normalised
 * cumulative histograms, @out will be a LUT that adjusts the PDF of the image
 * from which @in was made to match the PDF of @ref's image.
 *
 * See also: vips_maplut(), vips_hist_find(), vips_hist_norm(),
 * vips_hist_cum().
 *
 * Returns: 0 on success, -1 on error
 */
int
vips_hist_match(VipsImage *in, VipsImage *ref, VipsImage **out, ...)
{
	va_list ap;
	int result;

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

	return result;
}
