[Insight-developers] NumericTraits for RGBPixel

[Bradley Lowekamp]

Hello,

	ITK does not have max defined for any of the vector or array like  
classes either. I am pretty sure that this was done on purpose.

	From a theoretical point of view, a maximum is defined as the  
greatest element in a set. This essentially implies that the set can  
be ordered and have comparative operators. I don't think this is true  
for vector-like elements.

	Does the connected components algorithm need the max trait?

Brad

On Jan 14, 2009, at 9:18 AM, Gaëtan Lehmann wrote:

>
> Hi,
>
> I'm fixing the bug uncovered by Julien Michel in  
> ConnectedComponentImageFilter with RGB images as input, and want to  
> add a test for it.
> However, I can't succeed to build the modified test because  
> itk::NumericTraits< RGBPixelType< unsigned char > >::max() is not  
> defined.
> Is it done on purpose?
>
> Also, some functions defined in those numeric traits look suspicious  
> to me, like
>
>  typedef _TYPENAME_ NumericTraits<T>::RealType        
> ElementRealType; \
>  typedef RGBPixel<ElementRealType>         RealType; \
>  static const RealType max( const Self & a ) \
>    {  \
>      RealType b(a.Size());  \
>      b.Fill( NumericTraits< T >::max() ); \
>      return b; \
>    } \
>
> Why should max( const Self & a ) return a RealType? Why b inside the  
> function is filled with the size of a (which is always 3), and then  
> filled with zeros?
> For the scalar types, that function simply return the value of max().
>
> Regards,
>
> Gaëtan
>
>
> -- 
> Gaëtan Lehmann
> Biologie du Développement et de la Reproduction
> INRA de Jouy-en-Josas (France)
> tel: +33 1 34 65 29 66    fax: 01 34 65 29 09
> http://voxel.jouy.inra.fr  http://www.mandriva.org
> http://www.itk.org  http://www.clavier-dvorak.org
>
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========================================================
Bradley Lowekamp
Lockheed Martin Contractor for
Office of High Performance Computing and Communications
National Library of Medicine
blowekamp at mail.nih.gov


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