[Insight-users] multiple seed points in fast marching filter

[Dan Mueller]

Hi,

Fast Marching already supports multiple seed points.

You simply need to insert more nodes. For example:

  IndexType  seedPosition1;
  seedPosition1[0] = 10;
  seedPosition1[1] = 10;
  IndexType  seedPosition2;
  seedPosition2[0] = 20;
  seedPosition2[1] = 20;

  const double seedValue = 0.0;
  NodeType node1;
  node1.SetValue( seedValue );
  node1.SetIndex( seedPosition1 );
  NodeType node2;
  node2.SetValue( seedValue );
  node2.SetIndex( seedPosition2 );

  seeds->Initialize();
  seeds->InsertElement( 0, node1 );
  seeds->InsertElement( 1, node2 );
  fastMarching->SetTrialPoints( seeds );

Alternatively, here is a code snippet which sets trial points from a
binary image (may require some refactoring for your own purposes):

template <class TLevelSet, class TSpeedImage>
void
FastMarchingImageFilter<TLevelSet,TSpeedImage>
::SetTrialPointsFromImage( LabelImagePointer image )
{
  // Setup
  typedef ImageRegionConstIteratorWithIndex< LabelImageType > IteratorType;
  NodeContainer::Pointer nodes = NodeContainer::New();
  nodes->Initialize();
  IteratorType it( image, image->GetLargestPossibleRegion() );

  // Walk image
  unsigned int count = 0;
  for (it.GoToBegin(); !it.IsAtEnd(); ++it)
    {
    if (it.Get() > NumericTraits< LabelPixelType >::Zero)
      {
      NodeType node;
      node.SetIndex( it.GetIndex() );
      nodes->InsertElement( count, node );
      count++;
      }
    }

  // Set nodes
  this->SetTrialPoints( nodes );
  this->Modified();
}

HTH

Cheers, Dan

On 28 February 2011 18:32, Dhananjay244 <dhananjay.shah244 at gmail.com> wrote:
>
> hi,
> i am implementing the fastmarching algorithm as defined in itk:segmentation
> to extract the vertebral boundary in a X-ray. to successfully extract the
> vertebrae completely i need to mention multiple seed points to the filter,
> but the syntax for defining multiple seed points is not clear.
>
> if we cannot use multiple seeds points in the filter, then can anyone help
> me in modifying the code so as to read multiple seed points and perform
> fastmarching operation.
>
> thank you.
> --
> View this message in context: http://old.nabble.com/multiple-seed-points-in-fast-marching-filter-tp31031981p31031981.html
> Sent from the ITK - Users mailing list archive at Nabble.com.