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libvips/libvips/histogram/stdif.c

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/* statistical difference
*
* Copyright: 1990, N. Dessipris.
*
* Author: Nicos Dessipris
* Written on: 02/05/1990
* Modified on :
* 6/8/93 JC
* - now works for odd window sizes
* - ANSIfication
* 25/5/95 JC
* - new IM_ARRAY() macro
* 25/1/96 JC
* - im_lhisteq() adapted to make new im_stdif()
* - now partial, plus rolling window
* - 5x faster, amazingly
* - works
* 7/4/04
* - now uses im_embed() with edge stretching on the input, not
* the output
* 25/3/10
* - gtkdoc
* - small cleanups
* 10/8/13
* - wrapped as a class using hist_local.c
* - many bands
*/
/*
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 <vips/intl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <vips/vips.h>
typedef struct _VipsStdif {
VipsOperation parent_instance;
VipsImage *in;
VipsImage *out;
int width;
int height;
double a;
double m0;
double b;
double s0;
} VipsStdif;
typedef VipsOperationClass VipsStdifClass;
G_DEFINE_TYPE( VipsStdif, vips_stdif, VIPS_TYPE_OPERATION );
/* How ugly and stupid.
*/
#define MAX_BANDS (100)
static int
vips_stdif_generate( VipsRegion *or,
void *vseq, void *a, void *b, gboolean *stop )
{
VipsRect *r = &or->valid;
VipsRegion *ir = (VipsRegion *) vseq;
VipsImage *in = (VipsImage *) a;
VipsStdif *stdif = (VipsStdif *) b;
int bands = in->Bands;
int npel = stdif->width * stdif->width;
VipsRect irect;
int y;
int lsk;
int centre; /* Offset to move to centre of window */
/* What part of ir do we need?
*/
irect.left = or->valid.left;
irect.top = or->valid.top;
irect.width = or->valid.width + stdif->width;
irect.height = or->valid.height + stdif->height;
if( vips_region_prepare( ir, &irect ) )
return( -1 );
lsk = VIPS_REGION_LSKIP( ir );
centre = lsk * (stdif->height / 2) + stdif->width / 2;
for( y = 0; y < r->height; y++ ) {
/* Get input and output pointers for this line.
*/
VipsPel *p = VIPS_REGION_ADDR( ir, r->left, r->top + y );
VipsPel *q = VIPS_REGION_ADDR( or, r->left, r->top + y );
double f1 = stdif->a * stdif->m0;
double f2 = 1.0 - stdif->a;
double f3 = stdif->b * stdif->s0;
VipsPel *p1;
int x, i, j, b;
/* We will get int overflow for windows larger than about 256
* x 256, sadly.
*/
unsigned int sum[MAX_BANDS];
unsigned int sum2[MAX_BANDS];
/* Find sum, sum of squares for the start of this line.
*/
for( b = 0; b < bands; b++ ) {
memset( sum, 0, bands * sizeof( unsigned int ) );
memset( sum2, 0, bands * sizeof( unsigned int ) );
}
p1 = p;
for( j = 0; j < stdif->height; j++ ) {
i = 0;
for( x = 0; x < stdif->width; x++ ) {
for( b = 0; b < bands; b++ ) {
int t = p1[i++];
sum[b] += t;
sum2[b] += t * t;
}
}
p1 += lsk;
}
/* Loop for output pels.
*/
for( x = 0; x < r->width; x++ ) {
for( b = 0; b < bands; b++ ) {
/* Find stats.
*/
double mean = (double) sum[b] / npel;
double var = (double) sum2[b] / npel -
(mean * mean);
double sig = sqrt( var );
/* Transform.
*/
double res = f1 + f2 * mean +
((double) p[centre] - mean) *
(f3 / (stdif->s0 + stdif->b * sig));
/* And write.
*/
if( res < 0.0 )
*q++ = 0;
else if( res >= 256.0 )
*q++ = 255;
else
*q++ = res + 0.5;
/* Adapt sums - remove the pels from the left
* hand column, add in pels for a new
* right-hand column.
*/
p1 = p;
for( j = 0; j < stdif->height; j++ ) {
int t1 = p1[0];
int t2 = p1[bands * stdif->width];
sum[b] -= t1;
sum2[b] -= t1 * t1;
sum[b] += t2;
sum2[b] += t2 * t2;
p1 += lsk;
}
p += 1;
}
}
}
return( 0 );
}
static int
vips_stdif_build( VipsObject *object )
{
VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
VipsStdif *stdif = (VipsStdif *) object;
VipsImage **t = (VipsImage **) vips_object_local_array( object, 3 );
VipsImage *in;
if( VIPS_OBJECT_CLASS( vips_stdif_parent_class )->build( object ) )
return( -1 );
in = stdif->in;
if( vips_check_uncoded( class->nickname, in ) ||
vips_check_format( class->nickname, in, VIPS_FORMAT_UCHAR ) )
return( -1 );
if( stdif->width > in->Xsize ||
stdif->height > in->Ysize ) {
vips_error( class->nickname, "%s", _( "window too large" ) );
return( -1 );
}
if( in->Bands > MAX_BANDS ) {
vips_error( class->nickname, "%s", _( "too many bands" ) );
return( -1 );
}
/* Expand the input.
*/
if( vips_embed( in, &t[0],
stdif->width / 2, stdif->height / 2,
in->Xsize + stdif->width - 1, in->Ysize + stdif->height - 1,
"extend", VIPS_EXTEND_COPY,
NULL ) )
return( -1 );
in = t[0];
g_object_set( object, "out", vips_image_new(), NULL );
/* Set demand hints. FATSTRIP is good for us, as THINSTRIP will cause
* too many recalculations on overlaps.
*/
if( vips_image_pipelinev( stdif->out,
VIPS_DEMAND_STYLE_FATSTRIP, in, NULL ) )
return( -1 );
stdif->out->Xsize -= stdif->width - 1;
stdif->out->Ysize -= stdif->height - 1;
if( vips_image_generate( stdif->out,
vips_start_one,
vips_stdif_generate,
vips_stop_one,
in, stdif ) )
return( -1 );
stdif->out->Xoffset = 0;
stdif->out->Yoffset = 0;
return( 0 );
}
static void
vips_stdif_class_init( VipsStdifClass *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 = "stdif";
object_class->description = _( "statistical difference" );
object_class->build = vips_stdif_build;
VIPS_ARG_IMAGE( class, "in", 1,
_( "Input" ),
_( "Input image" ),
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET( VipsStdif, in ) );
VIPS_ARG_IMAGE( class, "out", 2,
_( "Output" ),
_( "Output image" ),
VIPS_ARGUMENT_REQUIRED_OUTPUT,
G_STRUCT_OFFSET( VipsStdif, out ) );
/* Windows larger than 256x256 will overflow sum2, see above.
*/
VIPS_ARG_INT( class, "width", 4,
_( "Width" ),
_( "Window width in pixels" ),
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET( VipsStdif, width ),
1, 256, 11 );
VIPS_ARG_INT( class, "height", 5,
_( "Height" ),
_( "Window height in pixels" ),
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET( VipsStdif, height ),
1, 256, 11 );
VIPS_ARG_DOUBLE( class, "a", 2,
_( "Mean weight" ),
_( "Weight of new mean" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsStdif, a ),
0.0, 1.0, 0.5 );
VIPS_ARG_DOUBLE( class, "m0", 2,
_( "Mean" ),
_( "New mean" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsStdif, m0 ),
-INFINITY, INFINITY, 128 );
VIPS_ARG_DOUBLE( class, "b", 2,
_( "Deviation weight" ),
_( "Weight of new deviation" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsStdif, b ),
0.0, 2.0, 0.5 );
VIPS_ARG_DOUBLE( class, "s0", 2,
_( "Deviation" ),
_( "New deviation" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsStdif, s0 ),
-INFINITY, INFINITY, 50 );
}
static void
vips_stdif_init( VipsStdif *stdif )
{
stdif->width = 11;
stdif->height = 11;
stdif->a = 0.5;
stdif->m0 = 128.0;
stdif->b = 0.5;
stdif->s0 = 50.0;
}
/**
* vips_stdif:
* @in: input image
* @out: output image
* @width: width of region
* @height: height of region
* @...: %NULL-terminated list of optional named arguments
*
* Optional arguments:
*
* @a: weight of new mean
* @m0: target mean
* @b: weight of new deviation
* @s0: target deviation
*
* vips_stdif() preforms statistical differencing according to the formula
* given in page 45 of the book "An Introduction to Digital Image
* Processing" by Wayne Niblack. This transformation emphasises the way in
* which a pel differs statistically from its neighbours. It is useful for
* enhancing low-contrast images with lots of detail, such as X-ray plates.
*
* At point (i,j) the output is given by the equation:
*
* vout(i,j) = @a * @m0 + (1 - @a) * meanv +
* (vin(i,j) - meanv) * (@b * @s0) / (@s0 + @b * stdv)
*
* Values @a, @m0, @b and @s0 are entered, while meanv and stdv are the values
* calculated over a moving window of size @width, @height centred on pixel
* (i,j). @m0 is the new mean, @a is the weight given to it. @s0 is the new
* standard deviation, @b is the weight given to it.
*
* Try:
*
* vips stdif $VIPSHOME/pics/huysum.v fred.v 0.5 128 0.5 50 11 11
*
* The operation works on one-band uchar images only, and writes a one-band
* uchar image as its result. The output image has the same size as the
* input.
*
* See also: vips_hist_local().
*
* Returns: 0 on success, -1 on error
*/
int
vips_stdif( VipsImage *in, VipsImage **out, int width, int height, ... )
{
va_list ap;
int result;
va_start( ap, height );
result = vips_call_split( "stdif", ap, in, out, width, height );
va_end( ap );
return( result );
}
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