[Insight-users] How to write CovariantVector Threshold Accessor with ITK?

[Melanie Uks]

Hi all,

I wanted to write a threshold accessor for vector pixels. I wanted to give
back a zero vector if one of the vector components, specified by the index,
is smaller than zero. Otherwise I wanted to give back the original vector. I
never worked with accessors but I checked the SoftwareGuide. So far I could
start a (non-working) example for this (see below). Can anybody tell me if
this is the right way to do such a thresholding with ITK and if yes how to
correct my example. At the moment I become the following error:
error C2440: 'static_cast' : cannot convert from
'itk::CovariantVector<T,NVectorDimension>' to 'float'

Thanks a lot!
Cheers,
Melanie


class ThresholdVectorPixelAccessor
{
public:
  typedef itk::CovariantVector<float,3>   InternalType;
  typedef                      float      InternalPixelType;
  typedef itk::CovariantVector<float,3>   ExternalType;

  void operator=( const ThresholdVectorPixelAccessor & vpa )
    {
      m_Index = vpa.m_Index;
    }
  ExternalType Get( const InternalType & input ) const
    {
    if(static_cast<InternalPixelType>( input[ m_Index ] ) < 0)
      {
          ExternalType empty;
          for(int i = 0; i < 3; i++)
              empty[i]=0;
          return empty;
      }
    else
        return static_cast<ExternalType>( input);
    }
  void SetIndex( unsigned int index )
    {
    m_Index = index;
    }
private:
  unsigned int m_Index;
};
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