[Insight-users] Re: CannyLevelSet Speed Image and Z(x)

[Luis Ibanez]

Hi Conn,


The speed image computation starts in :

      Insight/Code/Algorithms/
        itkSegmentationLevelSetimageFilter.txx

The computation is delegated to the SegmentationFunction
by invoking its method:

           CalculateSpeedImage();

This method is implemented in the file

      Insight/Code/Algorithms/
         itkCannySegmentationLevelSetFunction.txx

in lines 30-38.


The speed image is computed as a distance map to the Canny
edges in the method CalculateDistanceimage() in lines 81-102
of the same file.




    Regards,



       Luis



-----------------------------------------------------------------------------
conn sullivan wrote:

> Hello Luiz,
>  
> I appreciate your reply. I get the speed image now. I have one more 
> question. Are speed values taken directly from these speed image.  Also, 
> what is z(x) computed for canny edge filter.   What part of code from 
> .cxx file performs this calculation?
>  
> Thanks,
> Conn.
> 
> */Luis Ibanez <luis.ibanez at kitware.com>/* wrote:
> 
> 
>     Hi Conn,
> 
> 
>     Thanks for posting the output of the two readers.
> 
>     We tracked this problem down and found that what you are missing is
>     to invoke the "GenerateSpeedImage()" method in the Canny level set
>     filter before you invoke GetSpeedImage().
> 
>     Note that the GenerateSpeedImage() method must be called after
>     runninig the filter with Update().
> 
> 
>     For your convinience we added this code to the example in
> 
>     Insight/Examples/Segmentation/
>     CannySegmentationLevelSetImageFilter.cxx
> 
> 
> 
>     In order to get the new version simply update your CVS checkout of ITK,
>     or go to the CVS-Web portal and download the new version of this file:
> 
>     http://www.itk.org/cgi-bin/viewcvs.cgi/Examples/Segmentation/CannySegmentationLevelSetImageFilter.cxx?rev=1.27&root=Insight&view=log
> 
> 
> 
> 
>     Regards,
> 
> 
> 
>     Luis
> 
>