/* @(#)  Creates a Gaussian noisy float image with mean of 0 and variance of 1
 * @(#)  by averaging 12 random numbers
 * @(#)  Creates one band float image
 * @(#)  page 78 PIETGEN 1989 n = 12
 * @(#)   Usage
 * @(#) 
 * @(#) int im_gaussnoise(image, xsize, ysize, mean, sigma)
 * @(#) IMAGE *image;
 * @(#) int xsize, ysize;
 * @(#) double mean, sigma;
 * @(#)
 * @(#)  Returns 0 on success and -1 on error
 *
 * Copyright 1990, N. Dessipris.
 *
 * File written on 2/12/1986
 * Author : N. Dessipris
 * Updated : 6/6/1991
 * 21/7/93 JC
 *	- im_outcheck() call added
 * 1/2/95 JC
 *	- declaration for drand48() added
 *	- partialised, adapting im_black()
 * 23/10/98 JC
 *	- drand48() chaged to random() for poartability
 * 21/10/02 JC
 *	- tries rand() if random() is not available
 *	- uses RAND_MAX, d'oh
 */

/*

    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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  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 <vips/intl.h>

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

#include <vips/vips.h>

#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/

/* Keep parameters here.
 */
typedef struct {
	double mean;
	double sigma;
} GnoiseInfo;

/* Generate function --- just fill the region with noise. "dummy" is our
 * sequence value: we don't need one.
 */
/*ARGSUSED*/
static int
gnoise_gen( REGION *or, void *dummy, GnoiseInfo *gin )
{
	int x, y, i;
	int sz = IM_REGION_N_ELEMENTS( or );

	for( y = 0; y < or->valid.height; y++ ) {
		float *q = (float *) 
			IM_REGION_ADDR( or, or->valid.left, y + or->valid.top );

		for( x = 0; x < sz; x++ ) {
			double sum = 0.0;

			for( i = 0; i < 12; i++ ) 
#ifdef HAVE_RANDOM
				sum += (double) random() / RAND_MAX;
#else /*HAVE_RANDOM*/
#ifdef HAVE_RAND
				sum += (double) rand() / RAND_MAX;
#else /*HAVE_RAND*/
#error "no random number generator found"
#endif /*HAVE_RAND*/
#endif /*HAVE_RAND*/

			q[x] = (sum - 6.0) * gin->sigma + gin->mean;
		}
	}

	return( 0 );
}

/* Make a one band float image of gaussian noise.
 */
int
im_gaussnoise( IMAGE *out, int x, int y, double mean, double sigma )
{	
	GnoiseInfo *gin;

	/* Check parameters.
	 */
	if( x < 0 || y < 0 ) {
		im_errormsg( "im_gaussnoise: bad parameter" );
		return( -1 );
	}

	/* Check descriptor.
	 */
	if( im_poutcheck( out ) )
		return( -1 );
	
	/* Set fields.
	 */
	im_initdesc( out, 
		x, y, 1, 
		IM_BBITS_FLOAT, IM_BANDFMT_FLOAT, IM_CODING_NONE, IM_TYPE_B_W,
		1.0, 1.0, 0, 0 );

	/* Set hints - ANY is ok with us.
	 */
	if( im_demand_hint( out, IM_ANY, NULL ) )
		return( -1 );
	
	/* Save parameters.
	 */
	if( !(gin = IM_NEW( out, GnoiseInfo )) )
		return( -1 );
	gin->mean = mean;
	gin->sigma = sigma;

	/* Generate image.
	 */
	if( im_generate( out, NULL, gnoise_gen, NULL, gin, NULL ) )
		return( -1 );
	
	return( 0 );
}