[Insight-users] help with GradientVectorFlowImageFilter

[Kun]

Hi, all

I am trying to use GradientVectorFlowImageFilter to diffuse the gradient information to the whole image. The example code works well, but when I change the code, to diffuse the gradient as follows:

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#if defined(_MSC_VER)
#pragma warning ( disable : 4786 )
#endif
#include <itkImage.h>
#include <itkGradientRecursiveGaussianImageFilter.h>
#include <itkImageRegionIteratorWithIndex.h>
#include <itkCovariantVector.h>
#include <itkGradientImageFilter.h>
#include <itkGradientToMagnitudeImageFilter.h>
#include <itkDerivativeImageFilter.h>
#include <itkGradientVectorFlowImageFilter.h>
#include <itkLaplacianImageFilter.h>

#include "itkRecursiveGaussianImageFilter.h"

#include "itkImageFileWriter.h"

int main(int argc, char **argv)/**[])*/ 
{
  // Define the dimension of the images
  const unsigned int myDimension = 3;

  // Declare gradient type
  typedef itk::CovariantVector<double, myDimension> myGradientType;

  // Declare the types of the images
  typedef itk::Image<double, myDimension>           myImageType;
  typedef itk::Image<myGradientType, myDimension>   myGradientImageType;

  // Declare the type of the index to access images
  typedef itk::Index<myDimension>             myIndexType;

  // Declare the type of the size 
  typedef itk::Size<myDimension>              mySizeType;

  // Declare the type of the Region
  typedef itk::ImageRegion<myDimension>       myRegionType;

  typedef    itk::RecursiveGaussianImageFilter<myImageType,myImageType>    RecursiveGaussianImageFilterType;

  typedef itk::LaplacianImageFilter<myImageType, myImageType> myLaplacianFilterType;
  typedef itk::GradientVectorFlowImageFilter<myGradientImageType, myGradientImageType>
                                              myGVFFilterType;

  typedef itk::GradientImageFilter<myImageType, double, double>
                                              myGFilterType;

  typedef itk::GradientToMagnitudeImageFilter<myGradientImageType, myImageType>
                                              myGToMFilterType;
  // Create the image
  myImageType::Pointer inputImage  = myImageType::New();

  // Define their size, and start index
  mySizeType size;
  size[0] = 64;
  size[1] = 64;
  size[2] = 64;    

  myIndexType start;
  start.Fill(0);

  myRegionType region;
  region.SetIndex( start );
  region.SetSize( size );

  // Initialize Image A
  inputImage->SetLargestPossibleRegion( region );
  inputImage->SetBufferedRegion( region );
  inputImage->SetRequestedRegion( region );
  inputImage->Allocate();

  // Declare Iterator types apropriated for each image 
  typedef itk::ImageRegionIteratorWithIndex<myImageType>  myIteratorType;

  // Create one iterator for the Input Image A (this is a light object)
  myIteratorType it( inputImage, inputImage->GetRequestedRegion() );

  // Initialize the content of Image A
  std::cout << "Input Image initialization " << std::endl;
  
  it.GoToBegin();
  while( !it.IsAtEnd() ) 
  {
    it.Set( 0.0 );
    ++it;
  }

  size[0] = 32;
  size[1] = 32;
  size[2] = 32;    

  start[0] = 15;
  start[1] = 15;
  start[2] = 15;
  // Create one iterator for an internal region
  region.SetSize( size );
  region.SetIndex( start );
  myIteratorType itb( inputImage, region );
    
  itb.GoToBegin();
  // Initialize the content the internal region
  while( !itb.IsAtEnd() ) 
  {
    itb.Set( 100.0 );
    ++itb;
  }
  
  myGFilterType::Pointer f_Gradient    =    myGFilterType::New();
  f_Gradient->SetInput(inputImage);
  f_Gradient->Update();
  typedef    itk::ImageFileWriter<myGradientImageType>    VectorImageWriterType;
  VectorImageWriterType::Pointer    GradientWriter    =    VectorImageWriterType::New();
  GradientWriter->SetInput(f_Gradient->GetOutput());
  GradientWriter->SetFileName("Gradient.mha");
  GradientWriter->Update();

  myLaplacianFilterType::Pointer m_LFilter = myLaplacianFilterType::New();
  myGVFFilterType::Pointer m_GVFFilter = myGVFFilterType::New();

  m_GVFFilter->SetInput(f_Gradient->GetOutput());
  m_GVFFilter->SetLaplacianFilter(m_LFilter);
  m_GVFFilter->SetNoiseLevel(100);
  m_GVFFilter->SetTimeStep(0.002);
  m_GVFFilter->SetIterationNum(2);

  m_GVFFilter->Update();

  myGradientImageType::Pointer    m_GVF    =    m_GVFFilter->GetOutput();
  VectorImageWriterType::Pointer    writer2    =    VectorImageWriterType::New();
  writer2->SetInput(m_GVF);
  writer2->SetFileName("GGVF.mha");
  writer2->Update();

  return EXIT_SUCCESS;

}
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It seems that the GVF results is the same as the gradient filter. The grdient information is not diffused at all. 

Is there any errors when I use the GVF filter?

Thanks all.

Kun
   

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