[Insight-users] NeighborhoodOperator

[Joshua Cates]

Hi Franz,

In your case you would use the CreateToRadius() method and document that the 
CreateDirectional() is not valid for your operator.  You might consider throwing 
an exception if CreateDirectional() is called.

Josh.


l franz wrote:
> 
> 
> On 9/2/05, *Joshua Cates* <cates at sci.utah.edu 
> <mailto:cates at sci.utah.edu>> wrote:
> 
>     Hi Franz,
> 
>     There are, in fact, no such methods as GenerateScalarCoefficients() and
>     ScalarFill().  The documentation is in error.  You should implement
>     the methods
>     GenerateCoefficients() and Fill() instead.
> 
>     There is no requirement that the neighborhood operator be directional.
>     GenerateCoefficients() takes no input and returns a vector of the
>     coefficients
>     used in your operator.  Fill() takes that vector of coefficients as
>     the argument
>     and positions them spatially in the operator (which is, itself, a
>     neighborhood
>     data structure).
> 
>     For example, if you simply wanted to sum all of the values in a
>     neighborhood,
>     your GenerateCoefficients() method would return the vector
>     {1,1,1,1, ..., 1}.  The Fill() method would simply copy those values
>     into the
>     operator.
> 
>     Hope this helps,
> 
>     Josh.
> 
>     l franz wrote:
>      > Hi everybody,
>      >
>      > I want to create a neighborhood operator which inherits of
>      > "NeighborhoodOperator" class. My operator will weight each pixels
>     of a
>      > NDimensional neighborhood through a kind of inner product (the
>     output of
>      > this inner product will be a neighborhood with weighted pixels).
>     So my
>      > operator performs on all the neighborhood (and not in a particular
>      > direction) and its size is equal to the neighborhood size.
>      >
>      > So, my operator is not directional. In this case and if I understand
>      > well the documentation, I have to implement two methods:
>      > 1. GenerateScalarCoefficients
>      > 2. ScalarFill
>      >
>      > So, I don't need to implement the "GenerateCoefficients" and "Fill"
>      > methods (for directional operators) like in GaussianOperator or in
>      > DerivativeOperator.
>      >
>      > But, I don't know how to create the "GenerateScalarCoefficients" and
>      > "ScalarFill" methods. What do they have in input arguments? What
>     do they
>      > return? Do they have to call a particular method inherited from
>      > NeighborhoodOperator??
>      >
>      > I think that "GenerateScalarCoefficient" method is similar to
>      > "GenerateCoefficients" method. It takes no input argument and
>     return a
>      > "CoefficientVector" with the desired coefficients.
>      > But I have no ideas of how to implement the "ScalarFill" method.
>      >
>      > Does someone know about it? Or does anybody know where I can find an
>      > exemple of an non-directional neighborhood operator??
>      >
>      > Thanks,
>      > Cheers,
>      >
>      > Franz
>      >
>      >
>      >
>     ------------------------------------------------------------------------
> 
>      >
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> 
>     --
>     Josh Cates
>     SCI Institute / School of Computing
>     University of Utah
>     801-595-9165
>     http:/www.sci.utah.edu/~cates
> 
> 
> 
> Thanks for your help Josh. That light me a lot.
> 
> But I still have a little question. I have implemented a 
> "GenerateCoefficients()" and Fill()" methods. If I take in exemple the 
> way a directional operator (Gaussian or Derivative Operator) is used, 
> the coefficients are computed when the "CreateDirectional()" method is 
> called. This last method is inherited form the "NeighborhoodOperator" class.
> 
> In fact, the "CreateDirectional()" method will call the 
> "GenerateCoefficients()" and "Fill()" method that have been implemented. 
> But this "CreateDirectional()" method needs the "m_Direction" variable 
> (see NeighborhoodOperator.txx line 64). This last variable can be set by 
> the "SetDirection(unsigned int)" method.
> 
> In my case, I don't have a directional operator. So it's not 
> representative to set a direction.
> 
> So, have I the obligation to use the "CreateDirectional()" method to 
> generate the coefficients? Or perhaps another method (perhaps 
> "CreateToRadius" method).
> 
> And if I have to use the "CreateDirectional()" method, what would the 
> direction to set? Can I simply "forget" to set the direction? (I think 
> no...)
> 
> Thanks for your help,
> 
> Cheers,
> 
> Franz 
> 
> 
> 
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-- 
Josh Cates
SCI Institute / School of Computing
University of Utah
801-595-9165
http:/www.sci.utah.edu/~cates