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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 itkMeanImageFilter_hxx
#define itkMeanImageFilter_hxx
#include "itkBufferedImageNeighborhoodPixelAccessPolicy.h"
#include "itkImageNeighborhoodOffsets.h"
#include "itkImageRegionRange.h"
#include "itkIndexRange.h"
#include "itkNeighborhoodAlgorithm.h"
#include "itkOffset.h"
#include "itkShapedImageNeighborhoodRange.h"
#include "itkDefaultConvertPixelTraits.h"
namespace itk
{
template <typename TInputImage, typename TOutputImage>
MeanImageFilter<TInputImage, TOutputImage>::MeanImageFilter()
{
this->DynamicMultiThreadingOn();
}
template <typename TInputImage, typename TOutputImage>
void
MeanImageFilter<TInputImage, TOutputImage>::DynamicThreadedGenerateData(
const OutputImageRegionType & outputRegionForThread)
{
typename OutputImageType::Pointer output = this->GetOutput();
typename InputImageType::ConstPointer input = this->GetInput();
const auto radius = this->GetRadius();
// Find the data-set boundary "faces" and the center non-boundary subregion.
const auto calculatorResult =
NeighborhoodAlgorithm::ImageBoundaryFacesCalculator<InputImageType>::Compute(*input, outputRegionForThread, radius);
const auto neighborhoodOffsets = GenerateRectangularImageNeighborhoodOffsets<InputImageDimension>(radius);
// Process the non-boundary subregion, using a faster pixel access policy without boundary extrapolation.
GenerateDataInSubregion<BufferedImageNeighborhoodPixelAccessPolicy<InputImageType>>(
*input,
*output,
calculatorResult.GetNonBoundaryRegion(),
neighborhoodOffsets,
static_cast<InputPixelType *>(nullptr));
// Process each of the boundary faces. These are N-d regions which border
// the edge of the buffer.
for (const auto & boundaryFace : calculatorResult.GetBoundaryFaces())
{
GenerateDataInSubregion<ZeroFluxNeumannImageNeighborhoodPixelAccessPolicy<InputImageType>>(
*input, *output, boundaryFace, neighborhoodOffsets, static_cast<InputPixelType *>(nullptr));
}
}
template <typename TInputImage, typename TOutputImage>
template <typename TPixelAccessPolicy, typename TPixelType>
void
MeanImageFilter<TInputImage, TOutputImage>::GenerateDataInSubregion(
const TInputImage & inputImage,
TOutputImage & outputImage,
const ImageRegion<InputImageDimension> & imageRegion,
const std::vector<Offset<InputImageDimension>> & neighborhoodOffsets,
const TPixelType *)
{
const auto neighborhoodSize = static_cast<double>(neighborhoodOffsets.size());
auto neighborhoodRange = ShapedImageNeighborhoodRange<const InputImageType, TPixelAccessPolicy>(
inputImage, Index<InputImageDimension>(), neighborhoodOffsets);
auto outputIterator = ImageRegionRange<OutputImageType>(outputImage, imageRegion).begin();
for (const auto & index : ImageRegionIndexRange<InputImageDimension>(imageRegion))
{
neighborhoodRange.SetLocation(index);
auto sum = InputRealType{};
for (const InputPixelType pixelValue : neighborhoodRange)
{
sum += static_cast<InputRealType>(pixelValue);
}
// get the mean value
*outputIterator = static_cast<typename OutputImageType::PixelType>(sum / neighborhoodSize);
++outputIterator;
}
}
template <typename TInputImage, typename TOutputImage>
template <typename TPixelAccessPolicy, typename TValueType>
void
MeanImageFilter<TInputImage, TOutputImage>::GenerateDataInSubregion(
const TInputImage & inputImage,
TOutputImage & outputImage,
const ImageRegion<InputImageDimension> & imageRegion,
const std::vector<Offset<InputImageDimension>> & neighborhoodOffsets,
const VariableLengthVector<TValueType> *)
{
const auto neighborhoodSize = static_cast<double>(neighborhoodOffsets.size());
auto neighborhoodRange = ShapedImageNeighborhoodRange<const InputImageType, TPixelAccessPolicy>(
inputImage, Index<InputImageDimension>(), neighborhoodOffsets);
auto outputIterator = ImageRegionRange<OutputImageType>(outputImage, imageRegion).begin();
// These temp variable are needed outside the loop for
// VariableLengthVectors to avoid memory allocations on a per-pixel
// basis.
InputRealType sum(inputImage.GetNumberOfComponentsPerPixel());
OutputPixelType out(inputImage.GetNumberOfComponentsPerPixel());
for (const auto & index : ImageRegionIndexRange<InputImageDimension>(imageRegion))
{
neighborhoodRange.SetLocation(index);
using PixelComponentType = typename NumericTraits<InputRealType>::ValueType;
sum.Fill(NumericTraits<PixelComponentType>::Zero);
for (const InputPixelType pixelValue : neighborhoodRange)
{
sum += pixelValue;
}
sum /= neighborhoodSize;
// The following line is an implicit conversion from the
// InputRealType to the output pixel. If an explicit construction
// or static_cast was used a new VariableLengthVector temporary would be
// constructed requiring the array to be dynamic allocated. This
// implicit assignment reuses the array allocated in the variable out.
// *DO NOT USE static_cast*
out = sum;
*outputIterator = out;
++outputIterator;
}
}
} // end namespace itk
#endif
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