Examples/Iterators/ShapedNeighborhoodIterators2.cxx

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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.
 *
 *=========================================================================*/
 
// SoftwareGuide : BeginCommandLineArgs
//   INPUTS:  {BinaryImage.png}
//   OUTPUTS: {ShapedNeighborhoodIterators1b.png}
//   ARGUMENTS:    4
// SoftwareGuide : EndCommandLineArgs
 
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkConstShapedNeighborhoodIterator.h"
#include "itkImageRegionIterator.h"
#include "itkNeighborhoodAlgorithm.h"
#include <cmath>
 
int
main(int argc, char ** argv)
{
  if (argc < 4)
  {
    std::cerr << "Missing parameters. " << std::endl;
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0] << " inputImageFile outputImageFile element_radius"
              << std::endl;
    return EXIT_FAILURE;
  }
 
  using PixelType = unsigned char;
  using ImageType = itk::Image<PixelType, 2>;
  using ReaderType = itk::ImageFileReader<ImageType>;
 
  using ShapedNeighborhoodIteratorType =
    itk::ConstShapedNeighborhoodIterator<ImageType>;
  using IteratorType = itk::ImageRegionIterator<ImageType>;
 
  auto reader = ReaderType::New();
  reader->SetFileName(argv[1]);
 
  unsigned int element_radius = std::stoi(argv[3]);
 
  try
  {
    reader->Update();
  }
  catch (const itk::ExceptionObject & err)
  {
    std::cerr << "ExceptionObject caught !" << std::endl;
    std::cerr << err << std::endl;
    return EXIT_FAILURE;
  }
 
  auto output = ImageType::New();
  output->SetRegions(reader->GetOutput()->GetRequestedRegion());
  output->Allocate();
 
  using FaceCalculatorType =
    itk::NeighborhoodAlgorithm::ImageBoundaryFacesCalculator<ImageType>;
 
  FaceCalculatorType                         faceCalculator;
  FaceCalculatorType::FaceListType           faceList;
  FaceCalculatorType::FaceListType::iterator fit;
 
  ShapedNeighborhoodIteratorType::RadiusType radius;
  radius.Fill(element_radius);
 
  faceList =
    faceCalculator(reader->GetOutput(), output->GetRequestedRegion(), radius);
 
  IteratorType out;
  const auto   rad = static_cast<float>(element_radius);
 
  constexpr PixelType background_value = 0;
  constexpr PixelType foreground_value = 255;
 
  for (fit = faceList.begin(); fit != faceList.end(); ++fit)
  {
    ShapedNeighborhoodIteratorType it(radius, reader->GetOutput(), *fit);
    out = IteratorType(output, *fit);
 
    // Creates a circular structuring element by activating all the pixels
    // less than radius distance from the center of the neighborhood.
    for (float y = -rad; y <= rad; ++y)
    {
      for (float x = -rad; x <= rad; ++x)
      {
        ShapedNeighborhoodIteratorType::OffsetType off;
 
        float dis = std::sqrt(x * x + y * y);
        if (dis <= rad)
        {
          off[0] = static_cast<int>(x);
          off[1] = static_cast<int>(y);
          it.ActivateOffset(off);
        }
      }
    }
 
    // Software Guide : BeginLatex
    //
    // The logic of the inner loop can be rewritten to perform
    // dilation.  Dilation of the set $I$ by $E$ is the set of all $x$ such
    // that $E$ positioned at $x$ contains at least one element in $I$.
    //
    // Software Guide : EndLatex
 
    // Software Guide : BeginCodeSnippet
    // Implements dilation
    for (it.GoToBegin(), out.GoToBegin(); !it.IsAtEnd(); ++it, ++out)
    {
      ShapedNeighborhoodIteratorType::ConstIterator ci;
 
      bool flag = false;
      for (ci = it.Begin(); ci != it.End(); ++ci)
      {
        if (ci.Get() != background_value)
        {
          flag = true;
          break;
        }
      }
      if (flag == true)
      {
        out.Set(foreground_value);
      }
      else
      {
        out.Set(background_value);
      }
    }
  }
  // Software Guide : EndCodeSnippet
 
  // Software Guide : BeginLatex
  //
  // The output image is written and visualized directly as a binary image of
  // \code{unsigned chars}.  Figure~\ref{fig:ShapedNeighborhoodExample2}
  // illustrates some results of erosion and dilation on the image
  // \code{Examples/Data/BinaryImage.png}.  Applying erosion and dilation
  // in sequence effects the morphological operations of opening and closing.
  //
  // \begin{figure} \centering
  // \includegraphics[width=0.18\textwidth]{BinaryImage}
  // \includegraphics[width=0.18\textwidth]{ShapedNeighborhoodIterators1a}
  // \includegraphics[width=0.18\textwidth]{ShapedNeighborhoodIterators1b}
  // \includegraphics[width=0.18\textwidth]{ShapedNeighborhoodIterators1c}
  // \includegraphics[width=0.18\textwidth]{ShapedNeighborhoodIterators1d}
  // \itkcaption[Binary image morphology]{The effects of morphological
  // operations on a binary image using a circular structuring element of
  // size 4.  From left to right are the original image, erosion, dilation,
  // opening, and closing. The opening operation is erosion of the image
  // followed by dilation.  Closing is dilation of the image followed by
  // erosion.} \protect\label{fig:ShapedNeighborhoodExample2} \end{figure}
  //
  // Software Guide : EndLatex
 
  using WriterType = itk::ImageFileWriter<ImageType>;
 
  auto writer = WriterType::New();
  writer->SetFileName(argv[2]);
  writer->SetInput(output);
  try
  {
    writer->Update();
  }
  catch (const itk::ExceptionObject & err)
  {
    std::cerr << "ExceptionObject caught !" << std::endl;
    std::cerr << err << std::endl;
    return EXIT_FAILURE;
  }
 
  return EXIT_SUCCESS;
}