[Insight-users] Questions about computing distance map using FastMarchingImageFilter

[siyi ding]

Dear all,

 

I am trying to use the FastMarchingImageFilter to compute the distance map of a canny edge image. I could get correct distance map when I follow the example - just give one seed point. However, when I add all the none zero points(about 9000 points) in the canny image as seeds, the program becomes very slow and the result does not look like a correct distance map. Is there any one who could help about this?

 

Thanks a lot.







//////////////////////////////////////////////////////
 seeds->Initialize();

 NodeType node;
 const double seedValue = 0.0;
 int num_seeds = 0;

// If we only use one seed as below, we get the correct distance map of that point.
 /* 
 OutputImageType::IndexType  seedPosition;
 seedPosition[0] = 100;
 seedPosition[1] = 100;
 node.SetValue( seedValue );
 node.SetIndex( seedPosition );
 seeds->InsertElement(num_seeds++, node );


*/

 

// If we use all the nonzeros points in the canny edge image as seeds,we can not get correct distance map and the program is slow. 


 for (int i = 0; i< (image->w());i++)
  for (int j = 0; j< (image->h());j++)
  {
   OutputImageType::IndexType  seedPosition;
   seedPosition[0] = i;
   seedPosition[1] = j;
   
   if ( (CannyFilter->GetOutput()->GetPixel(seedPosition))>0)
   {
    node.SetValue( seedValue );
    node.SetIndex( seedPosition );
    seeds->InsertElement(num_seeds++, node );
   }
  }

 fastMarching->SetTrialPoints(  seeds  );
 fastMarching->SetSpeedConstant(1.0);
 fastMarching->SetOutputSize(  CannyFilter->GetOutput()->GetBufferedRegion().GetSize() );
 fastMarching->SetOutputOrigin ( CannyFilter->GetOutput()->GetOrigin());
 fastMarching->SetOutputSpacing ( CannyFilter->GetOutput()->GetSpacing());
 

const double stoppingTime = max(image->w(),image->h());  
 fastMarching->SetStoppingValue(  stoppingTime  );

 

FileWriterType::Pointer writer4 = FileWriterType::New();
    writer4->SetFileName("distance.jpg");
    writer4->UseCompressionOn();
  
 rescaleFilter->SetOutputMinimum(   0 );
 rescaleFilter->SetOutputMaximum( 255 );
 rescaleFilter->SetInput(  fastMarching->GetOutput()  );
 floatToUnsignedCharFilter ->SetInput( rescaleFilter->GetOutput() );
 writer4->SetInput( floatToUnsignedCharFilter->GetOutput() );
     
 try
    {
  writer4->Update();
  writer4->DebugOn();
    }
    catch (itk::ExceptionObject &e)
    {
    std::cerr << e << std::endl;
    }






Best,

Siyi Ding















Best,

Sylvia Siyi Ding



 

> Date: Thu, 1 Oct 2009 13:41:21 -0400
> From: mike.jackson at bluequartz.net
> To: insight-users at itk.org
> Subject: [Insight-users] Threaded Gaussian Filter
> 
> Anyone have a threaded version of the Gaussian Filter? I am currently
> using the example code for a Gaussian filter from the ITK distribution
> and for the image size I am throwing at it, the iteration loop takes a
> long time because it performs the filter serially on every pixel.
> 
> Thanks
> _________________________________________________________
> Mike Jackson mike.jackson at bluequartz.net
> BlueQuartz Software www.bluequartz.net
> Principal Software Engineer Dayton, Ohio
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