/* histogram normalisation
 *
 * Author: N. Dessipris
 * Written on: 02/08/1990
 * 24/5/95 JC
 *	- tidied up and ANSIfied
 * 20/7/95 JC
 *	- smartened up again
 *	- now works for hists >256 elements
 * 3/3/01 JC
 *	- broken into norm and norm ... helps im_histspec()
 *	- better behaviour for >8 bit hists
 * 31/10/05 JC
 * 	- was broken for vertical histograms, gah
 * 	- neater im_histnorm()
 * 23/7/07
 * 	- eek, off by 1 for more than 1 band hists
 * 12/5/08
 * 	- histnorm works for signed hists now as well
 * 24/3/10
 * 	- gtkdoc
 * 	- small cleanups
 * 12/8/13
 * 	- redone im_histnorm() as a class, vips_hist_norm()
 */

/*

	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 <vips/vips.h>

typedef struct _VipsHistNorm {
	VipsOperation parent_instance;

	VipsImage *in;
	VipsImage *out;
} VipsHistNorm;

typedef VipsOperationClass VipsHistNormClass;

G_DEFINE_TYPE(VipsHistNorm, vips_hist_norm, VIPS_TYPE_OPERATION);

static int
vips_hist_norm_build(VipsObject *object)
{
	VipsHistNorm *norm = (VipsHistNorm *) object;
	VipsImage **t = (VipsImage **) vips_object_local_array(object, 3);

	guint64 new_max;
	int bands;
	double *a, *b;
	int y;
	VipsBandFormat fmt;

	g_object_set(object, "out", vips_image_new(), NULL);

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

	/* Need max for each channel.
	 */
	if (vips_stats(norm->in, &t[0], NULL))
		return -1;

	/* Scale each channel by px / channel max
	 */
	new_max = VIPS_IMAGE_N_PELS(norm->in) - 1;
	bands = norm->in->Bands;
	if (!(a = VIPS_ARRAY(object, bands, double)) ||
		!(b = VIPS_ARRAY(object, bands, double)))
		return -1;
	for (y = 0; y < bands; y++) {
		a[y] = new_max / *VIPS_MATRIX(t[0], 1, y + 1);
		b[y] = 0;
	}

	if (vips_linear(norm->in, &t[1], a, b, bands, NULL))
		return -1;

	/* Make output format as small as we can.
	 */
	if (new_max <= 255)
		fmt = VIPS_FORMAT_UCHAR;
	else if (new_max <= 65535)
		fmt = VIPS_FORMAT_USHORT;
	else
		fmt = VIPS_FORMAT_UINT;

	if (vips_cast(t[1], &t[2], fmt, NULL) ||
		vips_image_write(t[2], norm->out))
		return -1;

	return 0;
}

static void
vips_hist_norm_class_init(VipsHistNormClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *object_class = (VipsObjectClass *) class;

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

	object_class->nickname = "hist_norm";
	object_class->description = _("normalise histogram");
	object_class->build = vips_hist_norm_build;

	VIPS_ARG_IMAGE(class, "in", 1,
		_("Input"),
		_("Input image"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsHistNorm, in));

	VIPS_ARG_IMAGE(class, "out", 2,
		_("Output"),
		_("Output image"),
		VIPS_ARGUMENT_REQUIRED_OUTPUT,
		G_STRUCT_OFFSET(VipsHistNorm, out));
}

static void
vips_hist_norm_init(VipsHistNorm *hist_norm)
{
}

/**
 * vips_hist_norm: (method)
 * @in: input image
 * @out: (out): output image
 * @...: %NULL-terminated list of optional named arguments
 *
 * Normalise histogram. The maximum of each band becomes equal to the maximum
 * index, so for example the max for a uchar image becomes 255.
 * Normalise each band separately.
 *
 * See also: vips_hist_cum().
 *
 * Returns: 0 on success, -1 on error
 */
int
vips_hist_norm(VipsImage *in, VipsImage **out, ...)
{
	va_list ap;
	int result;

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

	return result;
}
