[Insight-developers] ConditionalConstIterator Error?

[John M. Galeotti]

If I derive from ImageConstIterator, then I am forced to have a 
SetIndex method, which is ill-defined since multiple locations on a 
path can map to the same image index, and many image indices will not 
map to any point on a path.

So, should I try to descend from ImageConstIterator, 
ConditionalConstIterator, or nothing at all?

John

On Tuesday, April 15, 2003, at 10:08 PM, Luis Ibanez wrote:

>
> Hi John,
>
>
> It is not a problem that the path does not cover all
> the image. In fact, most iterator don't cove the full
> image since they are conditioned to walk over a region.
>
> You can safely derive your new iterator from the
> ImageConstIterator (or the ImageConstIteratorWithIndex).
>
> There is no advantage in deriving from the
> ConditionalConstIterator. As a matter of fact you just
> encountered that the conditional iterator has additional
> functionality that is not needed in your path iterator.
>
>
> Please note also that Josh recently added a chapter on
> iterators to the SoftwareGuide.pdf.
>
> Hope that helps
>
>
>    Luis
>
>
> --------------------------------------
> John M. Galeotti wrote:
>> Hello, I am working on an iterator to walk through an image following 
>> any type of path.  Since most paths will not cover all image indices, 
>> it would be logical for this iterator to descend from 
>> ConditionalConstIterator, but there is one small problem.  
>> ConditionalConstIterator includes the pure virtual function 
>> IsPixelIncluded(), which would be almost useless and prohibitively 
>> expensive to calculate for some types of paths (paths are almost 
>> always traveled linearly), and so I really do not want to implement 
>> the exhaustive search required for it.  The documentation in 
>> ConditionalConstIterator states that this function is used to 
>> "Compute whether the index of interest should be included in the 
>> flood."  Therefore, it seems that this pure virtual function should 
>> be introduced into the ITK class hierarchy in its child 
>> FloodFilledFunctionConditionalConstIterator, not in 
>> ConditionalConstIterator.  A quick look at the 
>> ConditionalConstIterator inheritance diagram seems to indicate that 
>> this would not be a problem, and 
>> FloodFilledFunctionConditionalConstIterator.h would not even have to 
>> be modified.
>> Could someone please remove the IsPixelIncluded() function from 
>> ConditionalConstIterator.h?
>> Thank you,
>> John Galeotti
>> jgaleotti@cmu.edu
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>
>
>
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