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/*=========================================================================
*
* Copyright NumFOCUS
*
* 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
*
* https://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 "itkImageRegionIteratorWithIndex.h"
#include "itkProgressReporter.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 has only a combination of 2,3, and 5 as prime factors.");
}
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);
OutputIndexValueType maxXIndex = inputIndex[0] + static_cast<OutputIndexValueType>(inputSize[0]);
unsigned int si = 0;
for (ImageRegionIteratorWithIndex<OutputImageType> oIt(outputPtr, outputPtr->GetLargestPossibleRegion());
!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;
}
} // namespace itk
#endif
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