/* @(#)  Function which averages the difference x_secondary[] - x_reference[]
 * @(#) and y_secondary[] - y_reference[] of the structure points;
 * @(#)  The rounded integer result is returned into dx, dy
 * @(#) No images are involved in this function.
 * @(#)
 * @(#) int vips__avgdxdy(points, dx, dy)
 * @(#) TiePoints *points;
 * @(#) int *dx, *dy;
 * @(#)
 * @(#) Returns 0 on success  and -1 on error.
 *
 * Copyright: 1990, N. Dessipris.
 *
 * Author: Nicos Dessipris
 * Written on: 20/12/1990
 * Modified on : 18/04/1991
 */

/*

	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 <math.h>

#include <vips/vips.h>

#include "pmosaicing.h"

int
vips__avgdxdy(TiePoints *points, int *dx, int *dy)
{
	int sumdx, sumdy;
	int i;

	if (points->nopoints == 0) {
		vips_error("vips__avgdxdy", "%s", _("no points to average"));
		return -1;
	}

	/* Lots of points.
	 */
	sumdx = 0;
	sumdy = 0;
	for (i = 0; i < points->nopoints; i++) {
		sumdx += points->x_secondary[i] - points->x_reference[i];
		sumdy += points->y_secondary[i] - points->y_reference[i];
	}

	*dx = VIPS_RINT((double) sumdx / (double) points->nopoints);
	*dy = VIPS_RINT((double) sumdy / (double) points->nopoints);

	return 0;
}
