[Insight-developers] ConstShapedNeighborhoodIterator inheritance

[Gaetan Lehmann]

Hi Joshua,

On Monday 10 October 2005 18:24, Joshua Cates wrote:
> Hi,
>
> The problem is that the ShapedNeighborhoodIterator does not maintain a
> pointer to a center pixel, so in the general case it is dangerous to
> expose this method. 

After a quick look at the code, I don't understand why you say that. 
ConstShapedNeighborhoodIterator is build on top of NeighborhoodIterator and 
call the methods of his ancestor to return the value. The difference is that 
there is a additional layer to handle the neighbors location.
The center pixel seems to be cached as well. Can you point me to the code 
which change the stored data ?

> If you need to access the center pixel, you can 
> include it in the neighborhood mask when you construct the iterator.  Of
> course, that requires that your application know which of the locations
> in the neighborhood is the center pixel.

This is a quite dirty solution: I don't need to have the center pixel in the 
neighborhood, so I will have to make a test to avoid compute it...

Isn't there a better (and easy) way to get the center pixel value ?

>
> Josh.
>
> Gaetan Lehmann wrote:
> > On Mon, 10 Oct 2005 00:39:37 +0200, Joshua Cates <cates at sci.utah.edu>
> >
> > wrote:
> >> Hi Gaetan,
> >>
> >> Superclass members are private where they don't make sense in the
> >> context of a neighborhood of arbitrary shape.  There is no guarantee,
> >> for example, that a ShapedNeighborhood has a center pixel.
> >
> > Are you sure it don't make sense to access the value of the center
> > pixel,  even if it is not in the neighborhood ?
> > There is lots of case where it make sense: Every time you need to look
> > at  the neighbors values to set the center pixel value, or everytime you
> > need  to compare the center pixel value and the neighbor value to set
> > the values  of the neighbors.
> > I have already used 5 iterators (!) only for the flooding part of a
> > morphological watershed, if the Set/GetCenterPixel() methods are not
> > available, I'll have to use 2 more iterators...
> >
> > Gaetan
> >
> >> Josh.
> >>
> >> On Oct 9, 2005, at 2:10 PM, Gaetan Lehmann wrote:
> >>> Hi,
> >>>
> >>> ConstShapedNeighborhoodIterator is a subclass of
> >>> NeighborhoodIterator.  Sadely,
> >>> all members of the superclass are private:
> >>>
> >>> class ITK_EXPORT ConstShapedNeighborhoodIterator
> >>>
> >>>   :  private NeighborhoodIterator<TImage, TBoundaryCondition>
> >>>
> >>> It prevent usage of Set/GetCenterPixel() methods, which  is really
> >>> annoying.
> >>> Is there a good reason to do that ?
> >>> Is it possible to switch to a public inheritance ?
> >>>
> >>> class ITK_EXPORT ConstShapedNeighborhoodIterator
> >>>
> >>>   :  public NeighborhoodIterator<TImage, TBoundaryCondition>
> >>>
> >>> Thanks,
> >>>
> >>> Gaetan
> >>> _______________________________________________
> >>> Insight-developers mailing list
> >>> Insight-developers at itk.org
> >>> http://www.itk.org/mailman/listinfo/insight-developers
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