libvips/libsrc/arithmetic/im_deviate.c

227 lines
4.9 KiB
C

/* @(#) Find the standard deviation of an image. Takes any non-complex image
* @(#) format, returns a double. Finds the deviation of all bands.
* @(#)
* @(#) int
* @(#) im_deviate( im, out )
* @(#) IMAGE *im;
* @(#) double *out;
* @(#)
* @(#) Returns 0 on success and -1 on error.
*
* Copyright: 1990, J. Cupitt
*
* Author: J. Cupitt
* Written on: 02/08/1990
* Modified on:
* 5/5/93 JC
* - now does partial images
* - less likely to overflow
* - adapted from im_avg
* 1/7/93 JC
* - adapted for partial v2
* - ANSIfied
* 21/2/95 JC
* - modernised again
* 11/5/95 JC
* - oops! return( NULL ) in im_avg(), instead of return( -1 )
* 20/6/95 JC
* - now returns double, not float
* 13/1/05
* - use 64 bit arithmetic
* 8/12/06
* - add liboil support
*/
/*
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 <assert.h>
#include <vips/vips.h>
#include <vips/internal.h>
#ifdef HAVE_LIBOIL
#include <liboil/liboil.h>
#endif /*HAVE_LIBOIL*/
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
/* Start function: allocate space for a pair of doubles in which we can
* accumulate the sum and the sum of squares.
*/
static void *
start_fn( IMAGE *out, void *a, void *b )
{
double *tmp;
if( !(tmp = IM_ARRAY( out, 2, double )) )
return( NULL );
tmp[0] = 0.0;
tmp[1] = 0.0;
return( (void *) tmp );
}
/* Stop function. Add this little sum to the main sum.
*/
static int
stop_fn( void *seq, void *a, void *b )
{
double *tmp = (double *) seq;
double *sum = (double *) a;
sum[0] += tmp[0];
sum[1] += tmp[1];
return( 0 );
}
/* Loop over region, adding information to the appropriate fields of tmp.
*/
static int
scan_fn( REGION *reg, void *seq, void *a, void *b )
{
double *tmp = (double *) seq;
Rect *r = &reg->valid;
IMAGE *im = reg->im;
int le = r->left;
int to = r->top;
int bo = IM_RECT_BOTTOM(r);
int sz = IM_REGION_N_ELEMENTS( reg );
double s = 0.0;
double s2 = 0.0;
int x, y;
/* Sum pels in this section.
*/
#define loop(TYPE) \
{ TYPE *p; \
\
for( y = to; y < bo; y++ ) { \
p = (TYPE *) IM_REGION_ADDR( reg, le, y ); \
\
for( x = 0; x < sz; x++ ) { \
TYPE v = p[x]; \
\
s += v; \
s2 += (double) v * (double) v; \
}\
}\
}
/* Now generate code for all types.
*/
switch( im->BandFmt ) {
case IM_BANDFMT_UCHAR: loop(unsigned char); break;
case IM_BANDFMT_CHAR: loop(signed char); break;
case IM_BANDFMT_USHORT: loop(unsigned short); break;
case IM_BANDFMT_SHORT: loop(signed short); break;
case IM_BANDFMT_UINT: loop(unsigned int); break;
case IM_BANDFMT_INT: loop(signed int); break;
case IM_BANDFMT_FLOAT: loop(float); break;
case IM_BANDFMT_DOUBLE:
#ifdef HAVE_LIBOIL
for( y = to; y < bo; y++ ) {
double *p = (double *) IM_REGION_ADDR( reg, le, y );
double t;
double t2;
oil_sum_f64( &t, p, sizeof( double ), sz );
oil_squaresum_f64( &t2, p, sz );
s += t;
s2 += t2;
}
#else /*!HAVE_LIBOIL*/
loop(double);
#endif /*HAVE_LIBOIL*/
break;
default:
assert( 0 );
}
/* Add to sum for this sequence.
*/
tmp[0] += s;
tmp[1] += s2;
return( 0 );
}
/* Find the average of an image.
*/
int
im_deviate( IMAGE *in, double *out )
{
double sum[2] = { 0.0, 0.0 };
gint64 N;
/* Check our args.
*/
if( im_pincheck( in ) )
return( -1 );
if( in->Coding != IM_CODING_NONE ) {
im_error( "im_deviate", _( "not uncoded" ) );
return( -1 );
}
if( im_iscomplex( in ) ) {
im_error( "im_deviate", _( "bad input type" ) );
return( -1 );
}
/* Loop over input, summing pixels.
*/
if( im_iterate( in, start_fn, scan_fn, stop_fn, &sum, NULL ) )
return( -1 );
/*
NOTE: NR suggests a two-pass algorithm to minimise roundoff.
But that's too expensive for us :-( so do it the old one-pass
way.
*/
/* Calculate and return deviation. Add a fabs to stop sqrt(<=0).
*/
N = (gint64) in->Xsize * in->Ysize * in->Bands;
*out = sqrt( fabs( sum[1] - (sum[0] * sum[0] / N) ) / (N - 1) );
return( 0 );
}