<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hello Michael,<div><br></div><div>Here is the declaration of one of the GetComponent methods:</div><div><br></div><div><div>template< typename T></div><div> typename EnableIfC<</div><div> IsSame<T, typename NumericTraits<T>::ValueType>::Value,</div><div> T >::Type</div><div> GetComponent(const T pix,</div><div> unsigned int itkNotUsed( idx ) ) const;</div></div><div><br></div><div>This uses the EnableIf idom to answer lets look at a simplification of function:</div><div><br></div><div><div>template< typename T> T GetComponent(const T pix, unsigned int idx ) const;</div></div><div><br></div><div>So I just simplified it some. So for function C++ has the ability to implicitly deduce the template parameters from the arguments passed to a function. So if you did the following:</div><div><br></div><div>int i;</div><div>GetComponent( i, 10 )</div><div><br></div><div>C++ can deduce the template parameter T, based on the function argument i being of type int.</div><div><br></div><div><br></div><div>There are a couple C++ tricks to overloading functions that should be considered before the EnableIf idiom should be considered. Using the EnableIf idom is really a last resort when simpler more understandable techniques can not be used.</div><div><br></div><div><br></div><div>Brad</div><div><br><div><div>On Aug 17, 2012, at 6:17 PM, Michael Stauffer wrote:</div><blockquote type="cite"><div>I'm using the new EnableIfC and DisableIfC routines, to try and optimize itkCentralDifferenceImageFunction::Evaluate* methods by specializing for scalar and vector pixel types. I have it working using my own SFINAE method I pulled off the web. But this, requires calling templated subfunctions, which cost about 2% in overhead.<br><br></div></blockquote><blockquote type="cite"><div><br>Looking at itkEnableIf.h and its usage in PatchBasedDenoisingImageFilter, I was hoping to be able to call the specialized Evalute* methods directly.<br><br><br>The method PatchBasedDenoisingImageFilter::GetComponent is are template-specialized to use one of two versions depending on whether the pixel is scalar or not. The method is templated.<br>But in PatchBasedDenoisingImageFilter::ComputeSignedEuclideanDifferenceAndWeightedSquaredNorm(), GetComponent is called without any template parameters. How does this work? I must be missing something.<br><br><br><br><br>template <br>void<br>PatchBasedDenoisingImageFilter<br>::ComputeSignedEuclideanDifferenceAndWeightedSquaredNorm(const PixelType& a, const PixelType& b,<br> const RealArrayType& weight,<br> bool itkNotUsed(useCachedComputations),<br> SizeValueType itkNotUsed(cacheIndex),<br> EigenValuesCacheType& itkNotUsed(eigenValsCache),<br> EigenVectorsCacheType& itkNotUsed(eigenVecsCache),<br> RealType& diff, RealArrayType& norm)<br>{<br> for (unsigned int pc = 0; pc < m_NumPixelComponents; ++pc)<br> {<br> RealValueType tmpDiff = GetComponent(b, pc) - GetComponent(a, pc);<br> RealValueType tmpWeight = weight[pc];<br> SetComponent(diff, pc, tmpDiff);<br> norm[pc] = tmpWeight * tmpWeight * tmpDiff * tmpDiff;<br> }<br>}<br><br></div></blockquote></div><br><div>
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