Examples/Iterators/ShapedNeighborhoodIterators2.cxx

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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
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 *         http://www.apache.org/licenses/LICENSE-2.0.txt
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 *  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>;

  ReaderType::Pointer reader = ReaderType::New();
  reader->SetFileName( argv[1] );

  unsigned int element_radius = ::std::stoi( argv[3] );

  try
    {
    reader->Update();
    }
  catch ( itk::ExceptionObject &err)
    {
    std::cerr << "ExceptionObject caught !" << std::endl;
    std::cerr << err << std::endl;
    return EXIT_FAILURE;
    }

  ImageType::Pointer 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 >;

  WriterType::Pointer writer = WriterType::New();
  writer->SetFileName( argv[2] );
  writer->SetInput( output );
  try
    {
    writer->Update();
    }
  catch ( itk::ExceptionObject &err)
    {
    std::cerr << "ExceptionObject caught !" << std::endl;
    std::cerr << err << std::endl;
    return EXIT_FAILURE;
    }

  return EXIT_SUCCESS;
}