/usr/include/ITK-4.5/itkGaussianOperator.hxx is in libinsighttoolkit4-dev 4.5.0-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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*
* 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 __itkGaussianOperator_hxx
#define __itkGaussianOperator_hxx
#include "itkGaussianOperator.h"
#include "itkOutputWindow.h"
#include "itkMacro.h"
namespace itk
{
template< typename TPixel, unsigned int VDimension, typename TAllocator >
typename GaussianOperator< TPixel, VDimension, TAllocator >
::CoefficientVector
GaussianOperator< TPixel, VDimension, TAllocator >
::GenerateCoefficients()
{
CoefficientVector coeff;
double sum;
int i;
int j;
typename CoefficientVector::iterator it;
const double et = vcl_exp(-m_Variance);
const double cap = 1.0 - m_MaximumError;
// Create the kernel coefficients as a std::vector
sum = 0.0;
coeff.push_back( et * ModifiedBesselI0(m_Variance) );
sum += coeff[0];
coeff.push_back( et * ModifiedBesselI1(m_Variance) );
sum += coeff[1] * 2.0;
for ( i = 2; sum < cap; i++ )
{
coeff.push_back( et * ModifiedBesselI(i, m_Variance) );
sum += coeff[i] * 2.0;
if ( coeff[i] <= 0.0 )
{
break; // failsafe
}
if ( coeff.size() > m_MaximumKernelWidth )
{
itkWarningMacro("Kernel size has exceeded the specified maximum width of "
<< m_MaximumKernelWidth << " and has been truncated to "
<< coeff.size()
<< " elements. You can raise the maximum width using the SetMaximumKernelWidth method.");
break;
}
}
// Normalize the coefficients so that their sum is one.
for ( it = coeff.begin(); it < coeff.end(); ++it )
{
*it /= sum;
}
// Make symmetric
j = static_cast< int >( coeff.size() ) - 1;
coeff.insert(coeff.begin(), j, 0);
for ( i = 0, it = coeff.end() - 1; i < j; --it, ++i )
{
coeff[i] = *it;
}
return coeff;
}
template< typename TPixel, unsigned int VDimension, typename TAllocator >
double
GaussianOperator< TPixel, VDimension, TAllocator >
::ModifiedBesselI0(double y)
{
const double d = vcl_fabs(y);
double accumulator;
if ( d < 3.75 )
{
double m = y / 3.75;
m *= m;
accumulator = 1.0 + m * ( 3.5156229 + m * ( 3.0899424 + m * ( 1.2067492
+ m
* ( 0.2659732 + m * ( 0.360768e-1 + m * 0.45813e-2 ) ) ) ) );
}
else
{
const double m = 3.75 / d;
accumulator = ( vcl_exp(d) / vcl_sqrt(d) ) * ( 0.39894228 + m * ( 0.1328592e-1
+ m
* ( 0.225319e-2 + m
* ( -0.157565e-2 + m * ( 0.916281e-2
+
m
* ( -0.2057706e-1
+ m
* ( 0.2635537e-1
+ m
* ( -
0.1647633e-1
+
m
*
0.392377e-2 ) ) ) ) ) ) ) );
}
return accumulator;
}
template< typename TPixel, unsigned int VDimension, typename TAllocator >
double
GaussianOperator< TPixel, VDimension, TAllocator >
::ModifiedBesselI1(double y)
{
const double d = vcl_fabs(y);
double accumulator;
if ( d < 3.75 )
{
double m = y / 3.75;
m *= m;
accumulator = d * ( 0.5 + m * ( 0.87890594 + m * ( 0.51498869 + m * ( 0.15084934
+ m
* ( 0.2658733e-1 + m
* ( 0.301532e-2 + m * 0.32411e-3 ) ) ) ) ) );
}
else
{
const double m = 3.75 / d;
accumulator = 0.2282967e-1 + m * ( -0.2895312e-1 + m * ( 0.1787654e-1
- m * 0.420059e-2 ) );
accumulator = 0.39894228 + m * ( -0.3988024e-1 + m * ( -0.362018e-2
+ m * ( 0.163801e-2 + m * ( -0.1031555e-1 + m * accumulator ) ) ) );
accumulator *= ( vcl_exp(d) / vcl_sqrt(d) );
}
if ( y < 0.0 )
{
return -accumulator;
}
else
{
return accumulator;
}
}
template< typename TPixel, unsigned int VDimension, typename TAllocator >
double
GaussianOperator< TPixel, VDimension, TAllocator >
::ModifiedBesselI(int n, double y)
{
const double ACCURACY = 40.0;
int j;
double qim, qi, qip, toy;
double accumulator;
if ( n < 2 )
{
throw ExceptionObject(__FILE__, __LINE__, "Order of modified bessel is > 2.", ITK_LOCATION); //
//
//
// placeholder
}
if ( y == 0.0 )
{
return 0.0;
}
else
{
toy = 2.0 / vcl_fabs(y);
qip = accumulator = 0.0;
qi = 1.0;
for ( j = 2 * ( n + (int)vcl_sqrt(ACCURACY * n) ); j > 0; j-- )
{
qim = qip + j * toy * qi;
qip = qi;
qi = qim;
if ( vcl_fabs(qi) > 1.0e10 )
{
accumulator *= 1.0e-10;
qi *= 1.0e-10;
qip *= 1.0e-10;
}
if ( j == n )
{
accumulator = qip;
}
}
accumulator *= ModifiedBesselI0(y) / qi;
if ( y < 0.0 && ( n & 1 ) )
{
return -accumulator;
}
else
{
return accumulator;
}
}
}
} // end namespace itk
#endif
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