SphinxExamples/src/Core/Common/UseParallelizeImageRegion/Code.cxx

/*=========================================================================
 *
 *  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.
 *
 *=========================================================================*/

#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkWatershedImageFilter.h"
#include "itkImageRegionIterator.h"

constexpr unsigned int Dimension = 2;
using InputPixelType = unsigned char;
using InputImageType = itk::Image< InputPixelType, Dimension >;
using OutputPixelType = itk::RGBAPixel< unsigned char >;
using OutputImageType = itk::Image< OutputPixelType, Dimension >;
using LabeledImageType = itk::Image< itk::IdentifierType, Dimension >;

OutputImageType::Pointer segmentationAndCustomColorization(InputImageType::Pointer inImage)
{
  typedef itk::WatershedImageFilter<InputImageType> WatershedFilterType;
  WatershedFilterType::Pointer watershed = WatershedFilterType::New();
  watershed->SetThreshold(0.05);
  watershed->SetLevel(0.3);
  watershed->SetInput(inImage);
  watershed->Update();

  LabeledImageType::Pointer image = watershed->GetOutput();
  image->DisconnectPipeline();

  OutputImageType::Pointer outImage = OutputImageType::New();
  outImage->CopyInformation(image);
  outImage->SetRegions(image->GetBufferedRegion());
  outImage->Allocate(true);

  itk::MultiThreaderBase::Pointer mt = itk::MultiThreaderBase::New();
  // ParallelizeImageRegion invokes the provided lambda function in parallel
  // each invocation will contain a piece of the overall region
  mt->ParallelizeImageRegion<Dimension>(image->GetBufferedRegion(),
      // the lambda will have access to outer variables 'image' and 'outImage'
      // it will have parameter 'region', which needs to be processed
      [image, outImage](const LabeledImageType::RegionType & region)
      {
        itk::ImageRegionConstIterator< LabeledImageType > iIt(image, region);
        itk::ImageRegionIterator< OutputImageType > oIt(outImage, region);
        for (; !iIt.IsAtEnd(); ++iIt, ++oIt)
          {
          LabeledImageType::IndexType ind = iIt.GetIndex();
          OutputPixelType p;
          p.SetAlpha(iIt.Get());
          static_assert(Dimension <= 3, "Dimension has to be 2 or 3");
          for (unsigned d = 0; d < Dimension; d++)
            {
            p.SetElement(d, ind[d]);
            }
          oIt.Set(p);
          }
      },
      nullptr); // we don't have a filter whose progress needs to be updated

  return outImage;
}

int main(int argc, char* argv[])
{
  if( argc != 3 )
    {
    std::cerr << "Usage: "<< std::endl;
    std::cerr << argv[0];
    std::cerr << " <InputFileName>";
    std::cerr << " <OutputFileName>" << std::endl;
    return EXIT_FAILURE;
    }

  using ReaderType = itk::ImageFileReader< InputImageType >;
  ReaderType::Pointer reader = ReaderType::New();
  reader->SetFileName(argv[1]);
  using WriterType = itk::ImageFileWriter< OutputImageType >;
  WriterType::Pointer writer = WriterType::New();
  writer->SetFileName(argv[2]);
  writer->UseCompressionOn();

  try
    {
    OutputImageType::Pointer outImage = segmentationAndCustomColorization(reader->GetOutput());
    writer->SetInput(outImage);
    writer->Update();
    }
  catch( itk::ExceptionObject & error )
    {
    std::cerr << "Error: " << error << std::endl;
    return EXIT_FAILURE;
    }

  return EXIT_SUCCESS;
}