/usr/include/ITK-4.9/itkShanbhagThresholdCalculator.hxx is in libinsighttoolkit4-dev 4.9.0-4ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 | /*=========================================================================
*
* Copyright Insight Software Consortium
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#ifndef itkShanbhagThresholdCalculator_hxx
#define itkShanbhagThresholdCalculator_hxx
#include "itkShanbhagThresholdCalculator.h"
#include "itkProgressReporter.h"
#include "vnl/vnl_math.h"
namespace itk
{
/*
* Compute the Shanbhag's threshold
*/
template<typename THistogram, typename TOutput>
void
ShanbhagThresholdCalculator<THistogram, TOutput>
::GenerateData(void)
{
const HistogramType * histogram = this->GetInput();
// histogram->Print(std::cout);
if ( histogram->GetTotalFrequency() == 0 )
{
itkExceptionMacro(<< "Histogram is empty");
}
ProgressReporter progress(this, 0, histogram->GetSize(0) );
if( histogram->GetSize(0) == 1 )
{
this->GetOutput()->Set( static_cast<OutputType>( histogram->GetMeasurement(0,0) ) );
}
unsigned int size = histogram->GetSize(0);
const double tolerance = 2.220446049250313E-16;
int threshold;
int ih, it;
int first_bin;
int last_bin;
double term;
double tot_ent; /* total entropy */
double min_ent; /* max entropy */
double ent_back; /* entropy of the background pixels at a given threshold */
double ent_obj; /* entropy of the object pixels at a given threshold */
std::vector<double> norm_histo(size); /* normalized histogram */
std::vector<double> P1(size); /* cumulative normalized histogram */
std::vector<double> P2(size);
int total = histogram->GetTotalFrequency();
for (ih = 0; (unsigned)ih < size; ih++ )
norm_histo[ih] = (double)histogram->GetFrequency(ih, 0)/total;
P1[0]=norm_histo[0];
P2[0]=1.0-P1[0];
for (ih = 1; (unsigned)ih < size; ih++ )
{
P1[ih]= P1[ih-1] + norm_histo[ih];
P2[ih]= 1.0 - P1[ih];
}
/* Determine the first non-zero bin */
first_bin=0;
for (ih = 0; (unsigned)ih < size; ih++ )
{
if ( !(std::abs(P1[ih])<tolerance))
{
first_bin = ih;
break;
}
}
/* Determine the last non-zero bin */
last_bin=size - 1;
for (ih = size - 1; ih >= first_bin; ih-- )
{
if ( !(std::abs(P2[ih])<tolerance))
{
last_bin = ih;
break;
}
}
// Calculate the total entropy each gray-level
// and find the threshold that maximizes it
threshold =-1;
min_ent = itk::NumericTraits<double>::max();
for ( it = first_bin; it <= last_bin; it++ )
{
/* Entropy of the background pixels */
ent_back = 0.0;
term = 0.5 / P1[it];
for ( ih = 1; ih <= it; ih++ )
{ //0+1?
ent_back -= norm_histo[ih] * std::log ( 1.0 - term * P1[ih - 1] );
}
ent_back *= term;
/* Entropy of the object pixels */
ent_obj = 0.0;
term = 0.5 / P2[it];
for ( ih = it + 1; (unsigned)ih < size; ih++ )
{
ent_obj -= norm_histo[ih] * std::log ( 1.0 - term * P2[ih] );
}
ent_obj *= term;
/* Total entropy */
tot_ent = std::abs ( ent_back - ent_obj );
if ( tot_ent < min_ent )
{
min_ent = tot_ent;
threshold = it;
}
}
this->GetOutput()->Set( static_cast<OutputType>( histogram->GetMeasurement( threshold, 0 ) ) );
}
} // end namespace itk
#endif
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