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/* estimate entropy
*
* Author: John Cupitt
* 11/8/15
* - from hist_ismonotonic.c
* 6/3/16
* - vips_log() call was mangled, thanks Lovell
*/
/*
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>
typedef struct _VipsHistEntropy {
VipsOperation parent_instance;
VipsImage *in;
double out;
} VipsHistEntropy;
typedef VipsOperationClass VipsHistEntropyClass;
G_DEFINE_TYPE( VipsHistEntropy, vips_hist_entropy,
VIPS_TYPE_OPERATION );
static int
vips_hist_entropy_build( VipsObject *object )
{
VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
VipsHistEntropy *entropy = (VipsHistEntropy *) object;
VipsImage **t = (VipsImage **) vips_object_local_array( object, 4 );
double avg;
double sum;
if( VIPS_OBJECT_CLASS( vips_hist_entropy_parent_class )->
build( object ) )
return( -1 );
if( vips_check_hist( class->nickname, entropy->in ) )
return( -1 );
/* Compute:
* norm_hist = hist / sum( hist )
* entropy = -sum( norm_hist * log2( norm_hist ) )
*/
if( vips_avg( entropy->in, &avg, NULL ) )
return( -1 );
sum = avg * VIPS_IMAGE_N_PELS( entropy->in ) * entropy->in->Bands;
if( vips_linear1( entropy->in, &t[0], 1.0 / sum, 0, NULL ) ||
vips_log( t[0], &t[1], NULL ) ||
vips_linear1( t[1], &t[2], 1.0 / log( 2.0 ), 0, NULL ) ||
vips_multiply( t[0], t[2], &t[3], NULL ) ||
vips_avg( t[3], &avg, NULL ) )
return( -1 );
g_object_set( entropy,
"out", -avg *
VIPS_IMAGE_N_PELS( entropy->in ) * entropy->in->Bands,
NULL );
return( 0 );
}
static void
vips_hist_entropy_class_init( VipsHistEntropyClass *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 = "hist_entropy";
object_class->description = _( "estimate image entropy" );
object_class->build = vips_hist_entropy_build;
VIPS_ARG_IMAGE( class, "in", 1,
_( "Input" ),
_( "Input histogram image" ),
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET( VipsHistEntropy, in ) );
VIPS_ARG_DOUBLE( class, "out", 2,
_( "Output" ),
_( "Output value" ),
VIPS_ARGUMENT_REQUIRED_OUTPUT,
G_STRUCT_OFFSET( VipsHistEntropy, out ),
-INFINITY, INFINITY, 0.0 );
}
static void
vips_hist_entropy_init( VipsHistEntropy *entropy )
{
}
/**
* vips_hist_entropy: (method)
* @in: input histogram
* @out: (out): image entropy
* @...: %NULL-terminated list of optional named arguments
*
* Estimate image entropy from a histogram. Entropy is calculated as:
*
* |[
* -sum( p * log2( p ) )
* ]|
*
* where p is histogram-value / sum-of-histogram-values.
*
* Returns: 0 on success, -1 on error
*/
int
vips_hist_entropy( VipsImage *in, double *out, ... )
{
va_list ap;
int result;
va_start( ap, out );
result = vips_call_split( "hist_entropy", ap, in, out );
va_end( ap );
return( result );
}
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