libvips/libsrc/other/im_meanstd.c

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2007-08-29 18:23:50 +02:00
/* @(#) Calculates the mean and the standard deviation (std) of
* @(#) an int or double buffer of size size.
* @(#)
* @(#) Usage:
* @(#) int im__mean_std_double_buffer(buffer, size, pmean, pstd)
* @(#) double *buffer;
* @(#) int size;
* @(#) double *pmean, *pstd;
* @(#)
* @(#) int im__mean_std_int_buffer(buffer, size, pmean, pstd)
* @(#) int *buffer;
* @(#) int size;
* @(#) double *pmean, *pstd;
* @(#)
* @(#) Both functions return 0 on success and -1 on error
*
* Copyright: N. Dessipris 1991
* Written on: 2/12/1991
* Updated on: 2/12/1991
* 22/7/93 JC
* - externs removed
*/
/*
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 <math.h>
#include <vips/vips.h>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
int
im__mean_std_double_buffer( double *buffer, int size,
double *pmean, double *pstd )
{
double mean, std;
register int i;
double sumf;
double temp;
double *pbuffer;
double sumf2;
double correction; /* calulates the correction term for the variance */
double variance; /* = (sumf2 - correction)/n */
if (size <= 0) {
im_errormsg("im_mean_std_double_buffer: wrong args");
return(-1);
}
mean = 0.0; std = 0.0;
sumf = 0.0; sumf2 = 0.0;
pbuffer = buffer;
for (i=0; i<size; i++) {
temp = *pbuffer++;
sumf += temp;
sumf2 += (temp*temp);
}
correction = (sumf * sumf)/((double)size);
mean = sumf/((double)size);
variance = ( sumf2 - correction)/((double)size);
std = sqrt(variance);
*pmean = mean;
*pstd = std;
return( 0 );
}
int
im__mean_std_int_buffer( int *buffer, int size,
double *pmean, double *pstd )
{
double mean, std;
register int i;
int sumf;
int temp;
int *pbuffer;
int sumf2;
double correction; /* calulates the correction term for the variance */
double variance; /* = (sumf2 - correction)/n */
if (size <= 0) {
im_errormsg("im_mean_std_int_buffer: wrong args");
return(-1);
}
mean = 0.0; std = 0.0;
sumf = 0; sumf2 = 0;
pbuffer = buffer;
for (i=0; i<size; i++) {
temp = *pbuffer++;
sumf += temp;
sumf2 += (temp*temp);
}
correction = ((double)(sumf * sumf))/((double)size);
mean = ((double)sumf)/((double)size);
variance = ( sumf2 - correction)/((double)size);
std = sqrt(variance);
*pmean = mean;
*pstd = std;
return(0);
}