[Insight-users] ITK Filters to generte Speed Image (Other than Sigmoid)

[conn sullivan]

Hello Luis,
 
What are the ITK filters other than Sigmoid that can be used to generate speed images?
In some cases, gradient magnitude + sidmoid filter is not helping me due to gaps produced on boundaries of gradient magnitude.  This leads to leackage in the final output. 
 
Thanks,
Conn
 


Luis Ibanez <luis.ibanez at kitware.com> wrote:


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 /* 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
> 
> 




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