Examples/Filtering/SurfaceExtraction.cxx

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//  Software Guide : BeginLatex
//
//  Surface extraction has attracted continuous interest since the early days
//  of image analysis, especially in the context of medical applications.
//  Although it is commonly associated with image segmentation, surface
//  extraction is not in itself a segmentation technique, instead it is a
//  transformation that changes the way a segmentation is represented. In its
//  most common form, isosurface extraction is the equivalent of image
//  thresholding followed by surface extraction.
//
//  Probably the most widely known method of surface extraction is the
//  \emph{Marching Cubes} algorithm~\cite{MarchingCubes}. Although it has been
//  followed by a number of variants~\cite{VTKBook}, Marching Cubes has become
//  an icon in medical image processing. The following example illustrates how
//  to perform surface extraction in ITK using an algorithm similar to
//  Marching Cubes~\footnote{Note that the Marching Cubes algorithm is covered
//  by a patent that expired on June 5th 2005.}.
//
//  Software Guide : EndLatex
 
 
#include "itkImageFileReader.h"
 
 
// Software Guide : BeginLatex
//
// The representation of unstructured data in ITK is done with
// the \doxygen{Mesh}. This class enables us to represent $N$-Dimensional
// grids of varied topology. It is natural for the filter that extracts
// surfaces from an image to produce a mesh as its output.
//
// We initiate our example by including the header files of the surface
// extraction filter, the image and the mesh.
//
// \index{Marching Cubes}
// \index{Isosurface extraction!Mesh}
// \index{BinaryMask3DMeshSource!Header}
// \index{Mesh!Isosurface extraction}
//
// Software Guide : EndLatex
 
// Software Guide : BeginCodeSnippet
#include "itkBinaryMask3DMeshSource.h"
#include "itkImage.h"
// Software Guide : EndCodeSnippet
 
 
int
main(int argc, char * argv[])
{
 
  if (argc < 3)
  {
    std::cerr << "Usage: IsoSurfaceExtraction  inputImageFile   objectValue "
              << std::endl;
    return EXIT_FAILURE;
  }
 
 
  // Software Guide : BeginLatex
  //
  // We define then the pixel type and dimension of the image from which we
  // are going to extract the surface.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  constexpr unsigned int Dimension = 3;
  using PixelType = unsigned char;
 
  using ImageType = itk::Image<PixelType, Dimension>;
  // Software Guide : EndCodeSnippet
 
 
  // Software Guide : BeginLatex
  //
  // With the same image type we instantiate the type of an ImageFileReader
  // and construct one with the purpose of reading in the input image.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using ReaderType = itk::ImageFileReader<ImageType>;
  ReaderType::Pointer reader = ReaderType::New();
  reader->SetFileName(argv[1]);
  // Software Guide : EndCodeSnippet
 
  try
  {
    reader->Update();
  }
  catch (const itk::ExceptionObject & exp)
  {
    std::cerr << "Exception thrown while reading the input file "
              << std::endl;
    std::cerr << exp << std::endl;
    return EXIT_FAILURE;
  }
 
 
  // Software Guide : BeginLatex
  //
  // The type of the \doxygen{Mesh} is instantiated by specifying the type to
  // be associated with the pixel value of the Mesh nodes. This particular
  // pixel type happens to be irrelevant for the purpose of extracting the
  // surface.
  //
  // \index{BinaryMask3DMeshSource!Instantiation}
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using MeshType = itk::Mesh<double>;
  // Software Guide : EndCodeSnippet
 
 
  // Software Guide : BeginLatex
  //
  // Having declared the Image and Mesh types we can now instantiate the
  // surface extraction filter, and construct one by invoking its \code{New()}
  // method.
  //
  // Software Guide : EndLatex
 
 
  // Software Guide : BeginCodeSnippet
  using MeshSourceType = itk::BinaryMask3DMeshSource<ImageType, MeshType>;
 
  MeshSourceType::Pointer meshSource = MeshSourceType::New();
  // Software Guide : EndCodeSnippet
 
 
  // Software Guide : BeginLatex
  //
  // In this example, the pixel value associated with the object
  // to be extracted is read from the command line arguments and it is passed
  // to the filter by using the \code{SetObjectValue()} method. Note that this
  // is different from the traditional isovalue used in the Marching Cubes
  // algorithm.  In the case of the \code{BinaryMask3DMeshSource} filter, the
  // object values define the membership of pixels to the object from which
  // the surface will be extracted. In other words, the surface will be
  // surrounding all pixels with value equal to the ObjectValue parameter.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  const auto objectValue = static_cast<PixelType>(std::stod(argv[2]));
 
  meshSource->SetObjectValue(objectValue);
  // Software Guide : EndCodeSnippet
 
 
  // Software Guide : BeginLatex
  //
  // The input to the surface extraction filter is taken from the output of
  // the image reader.
  //
  // \index{BinaryMask3DMeshSource!SetInput}
  //
  // Software Guide : EndLatex
 
 
  // Software Guide : BeginCodeSnippet
  meshSource->SetInput(reader->GetOutput());
  // Software Guide : EndCodeSnippet
 
 
  // Software Guide : BeginLatex
  //
  // Finally we trigger the execution of the pipeline by invoking the
  // \code{Update()} method. Given that the pipeline may throw an exception
  // this call must be place inside a \code{try/catch} block.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  try
  {
    meshSource->Update();
  }
  catch (const itk::ExceptionObject & exp)
  {
    std::cerr << "Exception thrown during Update() " << std::endl;
    std::cerr << exp << std::endl;
    return EXIT_FAILURE;
  }
  // Software Guide : EndCodeSnippet
 
 
  // Software Guide : BeginLatex
  //
  // We print out the number of nodes and cells in order to inspect the
  // output mesh.
  //
  // Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  std::cout << "Nodes = " << meshSource->GetNumberOfNodes() << std::endl;
  std::cout << "Cells = " << meshSource->GetNumberOfCells() << std::endl;
  // Software Guide : EndCodeSnippet
 
 
  // Software Guide : BeginLatex
  //
  // This resulting Mesh could be used as input for a deformable model
  // segmentation algorithm, or it could be converted to a format suitable for
  // visualization in an interactive application.
  //
  // Software Guide : EndLatex
 
 
  return EXIT_SUCCESS;
}