Examples/RegistrationITKv4/BSplineWarping1.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.
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 *  distributed under the License is distributed on an "AS IS" BASIS,
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//  Software Guide : BeginLatex
//
//  This example illustrates how to deform a 2D image using a
//  BSplineTransform.
//
//  \index{BSplineTransform}
//
//  Software Guide : EndLatex
 
 
// Software Guide : BeginCodeSnippet
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
 
#include "itkResampleImageFilter.h"
 
#include "itkBSplineTransform.h"
#include "itkTransformFileWriter.h"
 
//  Software Guide : EndCodeSnippet
 
#include <fstream>
 
//  The following section of code implements a Command observer
//  used to monitor the evolution of the registration process.
//
#include "itkCommand.h"
class CommandProgressUpdate : public itk::Command
{
public:
  using Self = CommandProgressUpdate;
  using Superclass = itk::Command;
  using Pointer = itk::SmartPointer<Self>;
  itkNewMacro(Self);
 
protected:
  CommandProgressUpdate() = default;
 
public:
  void
  Execute(itk::Object * caller, const itk::EventObject & event) override
  {
    Execute((const itk::Object *)caller, event);
  }
 
  void
  Execute(const itk::Object * object, const itk::EventObject & event) override
  {
    const auto * filter = static_cast<const itk::ProcessObject *>(object);
    if (!itk::ProgressEvent().CheckEvent(&event))
    {
      return;
    }
    std::cout << filter->GetProgress() << std::endl;
  }
};
 
 
int
main(int argc, char * argv[])
{
 
  if (argc < 5)
  {
    std::cerr << "Missing Parameters " << std::endl;
    std::cerr << "Usage: " << argv[0];
    std::cerr << " coefficientsFile fixedImage ";
    std::cerr << "movingImage deformedMovingImage" << std::endl;
    std::cerr << "[deformationField] [transformFile]" << std::endl;
    return EXIT_FAILURE;
  }
 
  //  Software Guide : BeginLatex
  //
  //  First, we define the necessary types for the fixed and moving images
  //  and image readers.
  //
  //  Software Guide: EndLatex
 
  // Software Guide : BeginCodeSnippet
  constexpr unsigned int ImageDimension = 2;
 
  using PixelType = unsigned char;
  using FixedImageType = itk::Image<PixelType, ImageDimension>;
  using MovingImageType = itk::Image<PixelType, ImageDimension>;
 
  using FixedReaderType = itk::ImageFileReader<FixedImageType>;
  using MovingReaderType = itk::ImageFileReader<MovingImageType>;
 
  using MovingWriterType = itk::ImageFileWriter<MovingImageType>;
  // Software Guide : EndCodeSnippet
 
  auto fixedReader = FixedReaderType::New();
  fixedReader->SetFileName(argv[2]);
 
  try
  {
    fixedReader->Update();
  }
  catch (const itk::ExceptionObject & excp)
  {
    std::cerr << "Exception thrown " << std::endl;
    std::cerr << excp << std::endl;
    return EXIT_FAILURE;
  }
 
 
  auto movingReader = MovingReaderType::New();
  auto movingWriter = MovingWriterType::New();
 
  movingReader->SetFileName(argv[3]);
  movingWriter->SetFileName(argv[4]);
 
 
  FixedImageType::ConstPointer fixedImage = fixedReader->GetOutput();
 
 
  using FilterType =
    itk::ResampleImageFilter<MovingImageType, FixedImageType>;
 
  auto resampler = FilterType::New();
 
  using InterpolatorType =
    itk::LinearInterpolateImageFunction<MovingImageType, double>;
 
  auto interpolator = InterpolatorType::New();
 
  resampler->SetInterpolator(interpolator);
 
  //  Software Guide : BeginLatex
  //
  //  Use the values from the fixed image to set the corresponding values
  //  in the resampler.
  //
  //  Software Guide : EndLatex
 
  //  Software Guide : BeginCodeSnippet
  FixedImageType::SpacingType   fixedSpacing = fixedImage->GetSpacing();
  FixedImageType::PointType     fixedOrigin = fixedImage->GetOrigin();
  FixedImageType::DirectionType fixedDirection = fixedImage->GetDirection();
 
  resampler->SetOutputSpacing(fixedSpacing);
  resampler->SetOutputOrigin(fixedOrigin);
  resampler->SetOutputDirection(fixedDirection);
 
 
  FixedImageType::RegionType fixedRegion = fixedImage->GetBufferedRegion();
  FixedImageType::SizeType   fixedSize = fixedRegion.GetSize();
  resampler->SetSize(fixedSize);
  resampler->SetOutputStartIndex(fixedRegion.GetIndex());
 
 
  resampler->SetInput(movingReader->GetOutput());
 
  movingWriter->SetInput(resampler->GetOutput());
  //  Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  We instantiate now the type of the \code{BSplineTransform} using
  //  as template parameters the type for coordinates representation, the
  //  dimension of the space, and the order of the B-spline.
  //
  //  \index{BSplineTransform!New}
  //  \index{BSplineTransform!Instantiation}
  //
  //  Software Guide : EndLatex
 
 
  // Software Guide : BeginCodeSnippet
  const unsigned int     SpaceDimension = ImageDimension;
  constexpr unsigned int SplineOrder = 3;
  using CoordinateRepType = double;
 
  using TransformType =
    itk::BSplineTransform<CoordinateRepType, SpaceDimension, SplineOrder>;
 
  auto bsplineTransform = TransformType::New();
  //  Software Guide : EndCodeSnippet
 
  //  Software Guide : BeginLatex
  //
  //  Next, fill the parameters of the B-spline transform using values from
  //  the fixed image and mesh.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  constexpr unsigned int numberOfGridNodes = 7;
 
  TransformType::PhysicalDimensionsType fixedPhysicalDimensions;
  TransformType::MeshSizeType           meshSize;
 
  for (unsigned int i = 0; i < SpaceDimension; ++i)
  {
    fixedPhysicalDimensions[i] =
      fixedSpacing[i] * static_cast<double>(fixedSize[i] - 1);
  }
  meshSize.Fill(numberOfGridNodes - SplineOrder);
 
  bsplineTransform->SetTransformDomainOrigin(fixedOrigin);
  bsplineTransform->SetTransformDomainPhysicalDimensions(
    fixedPhysicalDimensions);
  bsplineTransform->SetTransformDomainMeshSize(meshSize);
  bsplineTransform->SetTransformDomainDirection(fixedDirection);
 
 
  using ParametersType = TransformType::ParametersType;
  const unsigned int numberOfParameters =
    bsplineTransform->GetNumberOfParameters();
 
  const unsigned int numberOfNodes = numberOfParameters / SpaceDimension;
 
  ParametersType parameters(numberOfParameters);
  //  Software Guide : EndCodeSnippet
 
  //  Software Guide : BeginLatex
  //
  //  The B-spline grid should now be fed with coefficients at each node.
  //  Since this is a two-dimensional grid, each node should receive two
  //  coefficients. Each coefficient pair is representing a displacement
  //  vector at this node. The coefficients can be passed to the B-spline in
  //  the form of an array where the first set of elements are the first
  //  component of the displacements for all the nodes, and the second set of
  //  elements is formed by the second component of the displacements for all
  //  the nodes.
  //
  //  In this example we read such displacements from a file, but for
  //  convenience we have written this file using the pairs of $(x,y)$
  //  displacement for every node. The elements read from the file should
  //  therefore be reorganized when assigned to the elements of the array. We
  //  do this by storing all the odd elements from the file in the first block
  //  of the array, and all the even elements from the file in the second
  //  block of the array. Finally the array is passed to the B-spline
  //  transform using the \code{SetParameters()} method.
  //
  //  Software Guide : EndLatex
 
 
  // Software Guide : BeginCodeSnippet
  std::ifstream infile;
 
  infile.open(argv[1]);
 
  for (unsigned int n = 0; n < numberOfNodes; ++n)
  {
    infile >> parameters[n];
    infile >> parameters[n + numberOfNodes];
  }
 
  infile.close();
  //  Software Guide : EndCodeSnippet
 
  //  Software Guide : BeginLatex
  //
  //   Finally the array is passed to the B-spline transform using the
  //   \code{SetParameters()}.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  bsplineTransform->SetParameters(parameters);
  //  Software Guide : EndCodeSnippet
 
  auto observer = CommandProgressUpdate::New();
 
  resampler->AddObserver(itk::ProgressEvent(), observer);
 
 
  //  Software Guide : BeginLatex
  //
  //  At this point we are ready to use the transform as part of the resample
  //  filter. We trigger the execution of the pipeline by invoking
  //  \code{Update()} on the last filter of the pipeline, in this case writer.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  resampler->SetTransform(bsplineTransform);
 
  try
  {
    movingWriter->Update();
  }
  catch (const itk::ExceptionObject & excp)
  {
    std::cerr << "Exception thrown " << std::endl;
    std::cerr << excp << std::endl;
    return EXIT_FAILURE;
  }
  //  Software Guide : EndCodeSnippet
 
  using VectorType = itk::Vector<float, ImageDimension>;
  using DisplacementFieldType = itk::Image<VectorType, ImageDimension>;
 
  auto field = DisplacementFieldType::New();
  field->SetRegions(fixedRegion);
  field->SetOrigin(fixedOrigin);
  field->SetSpacing(fixedSpacing);
  field->SetDirection(fixedDirection);
  field->Allocate();
 
  using FieldIterator = itk::ImageRegionIterator<DisplacementFieldType>;
  FieldIterator fi(field, fixedRegion);
 
  fi.GoToBegin();
 
  TransformType::InputPointType    fixedPoint;
  TransformType::OutputPointType   movingPoint;
  DisplacementFieldType::IndexType index;
 
  VectorType displacement;
 
  while (!fi.IsAtEnd())
  {
    index = fi.GetIndex();
    field->TransformIndexToPhysicalPoint(index, fixedPoint);
    movingPoint = bsplineTransform->TransformPoint(fixedPoint);
    displacement = movingPoint - fixedPoint;
    fi.Set(displacement);
    ++fi;
  }
 
  using FieldWriterType = itk::ImageFileWriter<DisplacementFieldType>;
  auto fieldWriter = FieldWriterType::New();
 
  fieldWriter->SetInput(field);
 
  if (argc >= 6)
  {
    fieldWriter->SetFileName(argv[5]);
    try
    {
      fieldWriter->Update();
    }
    catch (const itk::ExceptionObject & excp)
    {
      std::cerr << "Exception thrown " << std::endl;
      std::cerr << excp << std::endl;
      return EXIT_FAILURE;
    }
  }
 
  if (argc >= 7)
  {
    fieldWriter->SetFileName(argv[6]);
    try
    {
      using TransformWriterType = itk::TransformFileWriter;
      auto transformWriter = TransformWriterType::New();
      transformWriter->AddTransform(bsplineTransform);
      transformWriter->SetFileName(argv[6]);
      transformWriter->Update();
    }
    catch (const itk::ExceptionObject & excp)
    {
      std::cerr << "Exception thrown " << std::endl;
      std::cerr << excp << std::endl;
      return EXIT_FAILURE;
    }
  }
 
  return EXIT_SUCCESS;
}