160 lines
3.8 KiB
C
160 lines
3.8 KiB
C
/* estimate entropy
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*
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* Author: John Cupitt
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* 11/8/15
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* - from hist_ismonotonic.c
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* 6/3/16
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* - vips_log() call was mangled, thanks Lovell
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*/
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/*
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This file is part of VIPS.
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VIPS is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA
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*/
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/*
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These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif /*HAVE_CONFIG_H*/
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#include <glib/gi18n-lib.h>
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#include <stdio.h>
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#include <math.h>
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#include <vips/vips.h>
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typedef struct _VipsHistEntropy {
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VipsOperation parent_instance;
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VipsImage *in;
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double out;
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} VipsHistEntropy;
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typedef VipsOperationClass VipsHistEntropyClass;
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G_DEFINE_TYPE( VipsHistEntropy, vips_hist_entropy,
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VIPS_TYPE_OPERATION );
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static int
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vips_hist_entropy_build( VipsObject *object )
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{
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VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
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VipsHistEntropy *entropy = (VipsHistEntropy *) object;
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VipsImage **t = (VipsImage **) vips_object_local_array( object, 4 );
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double avg;
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double sum;
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if( VIPS_OBJECT_CLASS( vips_hist_entropy_parent_class )->
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build( object ) )
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return( -1 );
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if( vips_check_hist( class->nickname, entropy->in ) )
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return( -1 );
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/* Compute:
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* norm_hist = hist / sum( hist )
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* entropy = -sum( norm_hist * log2( norm_hist ) )
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*/
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if( vips_avg( entropy->in, &avg, NULL ) )
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return( -1 );
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sum = avg * VIPS_IMAGE_N_PELS( entropy->in ) * entropy->in->Bands;
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if( vips_linear1( entropy->in, &t[0], 1.0 / sum, 0, NULL ) ||
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vips_log( t[0], &t[1], NULL ) ||
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vips_linear1( t[1], &t[2], 1.0 / log( 2.0 ), 0, NULL ) ||
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vips_multiply( t[0], t[2], &t[3], NULL ) ||
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vips_avg( t[3], &avg, NULL ) )
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return( -1 );
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g_object_set( entropy,
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"out", -avg *
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VIPS_IMAGE_N_PELS( entropy->in ) * entropy->in->Bands,
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NULL );
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return( 0 );
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}
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static void
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vips_hist_entropy_class_init( VipsHistEntropyClass *class )
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{
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GObjectClass *gobject_class = G_OBJECT_CLASS( class );
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VipsObjectClass *object_class = (VipsObjectClass *) class;
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gobject_class->set_property = vips_object_set_property;
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gobject_class->get_property = vips_object_get_property;
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object_class->nickname = "hist_entropy";
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object_class->description = _( "estimate image entropy" );
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object_class->build = vips_hist_entropy_build;
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VIPS_ARG_IMAGE( class, "in", 1,
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_( "Input" ),
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_( "Input histogram image" ),
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VIPS_ARGUMENT_REQUIRED_INPUT,
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G_STRUCT_OFFSET( VipsHistEntropy, in ) );
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VIPS_ARG_DOUBLE( class, "out", 2,
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_( "Output" ),
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_( "Output value" ),
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VIPS_ARGUMENT_REQUIRED_OUTPUT,
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G_STRUCT_OFFSET( VipsHistEntropy, out ),
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-INFINITY, INFINITY, 0.0 );
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}
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static void
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vips_hist_entropy_init( VipsHistEntropy *entropy )
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{
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}
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/**
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* vips_hist_entropy: (method)
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* @in: input histogram
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* @out: (out): image entropy
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* @...: %NULL-terminated list of optional named arguments
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*
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* Estimate image entropy from a histogram. Entropy is calculated as:
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*
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* |[
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* -sum( p * log2( p ) )
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* ]|
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*
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* where p is histogram-value / sum-of-histogram-values.
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*
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* Returns: 0 on success, -1 on error
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*/
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int
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vips_hist_entropy( VipsImage *in, double *out, ... )
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{
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va_list ap;
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int result;
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va_start( ap, out );
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result = vips_call_split( "hist_entropy", ap, in, out );
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va_end( ap );
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return( result );
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}
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