[Insight-users] how to change propagation speed in segmentationlevelsetfunction class?

[Luis Ibanez]

Hi Ning,


It is not surprising that your code changes didn't have any effect
in the results of the segmentation.


Your line for looking at the pixels of the new m_PropImage is only
used if the pixel in question is *outside* of the current speed image.


Since very often the speed image has the same support as the feature
image, then it is very unlikely that your m_PropImage will ever be
actually queried for pixel values.


What you probably want to do is to connect your m_PropImage to the
interpolator that now is connected to the Speed image, and then
remove the "else" that you added to the if( IsInsideBuffer).
In this way, your m_PropImage will replace the m_Speed image.


The replacement of the input to the interpolator should be made
in lines 29 and 63.


    Regards,



       Luis




-----------------
ning qian wrote:
> 
> Hi, all, I just started hacking in itk. I am trying to change the 
> propagation speed in segmentation levelset. I derived my class from 
> segmentationlevelsetfunction and defined my PropagationSpeed() function 
> as follows:
> 
> PropagationSpeed(const NeighborhoodType &neighborhood,
>                   const FloatOffsetType &offset, GlobalDataStruct *) const
> {
>  IndexType idx = neighborhood.GetIndex();
>  ContinuousIndexType cdx;
>  for (unsigned i = 0; i < ImageDimension; ++i)
>    {
>    cdx[i] = static_cast<double>(idx[i]) - offset[i];
>    }
>  if ( m_Interpolator->IsInsideBuffer(cdx) )
>    {
>    return (static_cast<ScalarValueType>(
>              m_Interpolator->EvaluateAtContinuousIndex(cdx)));
>    }
>  else return ( static_cast<ScalarValueType>(m_PropImage->GetPixel(idx)) );
> }
> 
> 
> where m_PropImage is a new member I defined for the propagation speed. 
> But when I ran the simulation using examples, it seems that the results 
> did not change at all as using originally defined m_SpeedImage. Besides 
> this change, do I need to make any other modifications?
> 
> Thanks a lot for your help.
> 
> Best, Ning
> 
> 
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