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1. Gradient vector field

2. Anisotropic diffusion of gradient vector

3. Gradient vector flow

4. Hessian matrix



I calculate the gradientimage using itkGradientImageFilter. I use
itkGradientVectorFlowImageFilter

to directly calculate the gradient vector flow as it is given the diffusion
is already inbuilt in

itkGradientVectorFlowImageFilter.



I use QVTK for visualisation. The image is loaded as vtk image. To apply

itk algorithm, i convert the vtk image to itk image using vtkKWEITKImage.cxx

from vtkedge. The same file is used for itk image to vtk image for display.



typedef itk::Image< T, 3 >   InputImageType; //input image type

typedef itk::Image< float, 3 >   OutputImageType; //outputimage type



/// cast filter which converts any inputimage type to outputimage type

typedef itk::CastImageFilter <InputImageType, OutputImageType> castType;

castType::Pointer castfilter = castType::New();



// image is vtkKWEITKImage object

castfilter->SetInput( dynamic_cast< InputImageType * >( image->GetITKImage()
) );



//itk vector image declaration

typedef itk::CovariantVector<float, 3> VectorPixelType;

typedef itk::Image<VectorPixelType, 3> VectorImageType;



//calculate the gradient vector of image

typedef itk::GradientImageFilter <OutputImageType, float, float>
GradientType;

GradientType::Pointer gradient = GradientType::New();

gradient->SetInput(castfilter->GetOutput());

gradient->Update();



//calculation of gradient vector flow from diffused gradient vector

typedef itk::GradientVectorFlowImageFilter<VectorImageType, VectorImageType,
double> VectorFlowType;

VectorFlowType::Pointer flowfilter = VectorFlowType::New();

flowfilter->SetInput(gradient->GetOutput());



//observer of algorithm execution for time

p->Observe( flowfilter );



//the image object is updated with output image from flowfilter

image->SetImage( flowfilter->GetOutput( ) );

image->Modified();



flowfilter->ReleaseDataFlagOn();

return EXIT_SUCCESS;



Questions:



1. I would like to know whether itkGradientVectorFlowImageFilter computes
anisotropic diffusion or gaussian diffusion ?



2. I want to visualise the gradient vector flow as arrows. How can i achieve
this visualisation?



3. If there is any example, which would help me fully or partially I would
like to know.



Thank you in advance.



Regards,

Kana



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Please keep messages on-topic and check the ITK FAQ at:
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<p>Alberto G&oacute;mez</p>
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<i>Division of Imaging Sciences <br>
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<p>phone: +44 (0) 20 718 88364<br>
email: <a href="mailto:alberto.gomez at kcl.ac.uk">alberto.gomez at kcl.ac.uk</a>
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