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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 itkVnlHalfHermitianToRealInverseFFTImageFilter_hxx
#define itkVnlHalfHermitianToRealInverseFFTImageFilter_hxx
#include "itkHalfHermitianToRealInverseFFTImageFilter.hxx"
#include "itkImageRegionIteratorWithIndex.h"
#include "itkProgressReporter.h"
#include "itkVnlHalfHermitianToRealInverseFFTImageFilter.h"
namespace itk
{
template< typename TInputImage, typename TOutputImage >
void
VnlHalfHermitianToRealInverseFFTImageFilter< TInputImage, TOutputImage >
::GenerateData()
{
// Get pointers to the input and output.
typename InputImageType::ConstPointer inputPtr = this->GetInput();
typename OutputImageType::Pointer outputPtr = this->GetOutput();
if ( !inputPtr || !outputPtr )
{
return;
}
// We don't have a nice progress to report, but at least this simple line
// reports the beginning and the end of the process.
ProgressReporter progress( this, 0, 1 );
const InputSizeType inputSize = inputPtr->GetLargestPossibleRegion().GetSize();
const InputIndexType inputIndex = inputPtr->GetLargestPossibleRegion().GetIndex();
const OutputSizeType outputSize = outputPtr->GetLargestPossibleRegion().GetSize();
const OutputIndexType outputIndex = outputPtr->GetLargestPossibleRegion().GetIndex();
// Allocate output buffer memory
outputPtr->SetBufferedRegion( outputPtr->GetRequestedRegion() );
outputPtr->Allocate();
unsigned int vectorSize = 1;
for ( unsigned int i = 0; i < ImageDimension; i++ )
{
if ( !VnlFFTCommon::IsDimensionSizeLegal( outputSize[i] ) )
{
itkExceptionMacro(<< "Cannot compute FFT of image with size "
<< outputSize << ". VnlHalfHermitianToRealInverseFFTImageFilter operates "
<< "only on images whose size in each dimension is a multiple of "
<< "2, 3, or 5." );
}
vectorSize *= outputSize[i];
}
// VNL requires the full complex result of the transform, so we
// produce it here from the half complex image assumed when the output is real.
SignalVectorType signal( vectorSize );
ImageRegionIteratorWithIndex< OutputImageType > oIt( outputPtr,
outputPtr->GetLargestPossibleRegion() );
OutputIndexValueType maxXIndex = inputIndex[0] +
static_cast< OutputIndexValueType >( inputSize[0] );
unsigned int si = 0;
for (oIt.GoToBegin(); !oIt.IsAtEnd(); ++oIt)
{
typename OutputImageType::IndexType index = oIt.GetIndex();
if ( index[0] >= maxXIndex )
{
// Flip the indices in each dimension
for (unsigned int i = 0; i < ImageDimension; ++i)
{
if ( index[i] != outputIndex[i] )
{
index[i] = outputSize[i] - index[i] + 2 * outputIndex[i];
}
}
signal[si] = std::conj( inputPtr->GetPixel( index ) );
}
else
{
signal[si] = inputPtr->GetPixel( index );
}
si++;
}
OutputPixelType *out = outputPtr->GetBufferPointer();
// call the proper transform, based on compile type template parameter
VnlFFTCommon::VnlFFTTransform< OutputImageType > vnlfft( outputSize );
vnlfft.transform( signal.data_block(), 1 );
// Copy the VNL output back to the ITK image. Extract the real part
// of the signal. Ideally, the normalization by the number of
// elements should have been accounted for by the VNL inverse
// Fourier transform, but it is not. So, we take care of it by
// dividing the signal by the vectorSize.
for ( unsigned int i = 0; i < vectorSize; i++ )
{
out[i] = signal[i].real() / vectorSize;
}
}
template< typename TInputImage, typename TOutputImage >
SizeValueType
VnlHalfHermitianToRealInverseFFTImageFilter< TInputImage, TOutputImage >
::GetSizeGreatestPrimeFactor() const
{
return VnlFFTCommon::GREATEST_PRIME_FACTOR;
}
}
#endif
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