[Insight-developers] problem with iterator

[Luis Ibanez]

Hi Martin,

Please see comments below:

On Thu, Nov 18, 2010 at 10:37 AM, Martin Waitzbauer <mazzok at gmx.at> wrote:

> Hi there, i think i have  aproblem with understanding the iterators
> orrectly
>
> im oading a 3d dataset with 256(X)x256(Y)x124(Z)
>
> I wanted to check if i was understanding the iterator behavior correctly by
> iterating throught al the slices
> this can be done with
> InputIteratorType it(input,input->GetLargestPossibleRegion());
>
> since i want to acces the slies individually i tried
> InputImageType::RegionType reg;
> InputImageType::RegionType::SizeType size;
> InputImageType::RegionType::IndexType index;
> size[0] = 100;
> size[1] = 100;
>

You are missing to initialize:    size[2]

These two variables will contain garbage
from memory and will mislead your
interpretation of the iterator behavior....



> index[0] = 0;
> index[1] = 0;
>
for(int j =0; j < Z_Depth;j++){
>        index[2] = j;
>        reg.SetSize(size);
>        reg.SetIndex(index);
>        InputIteratorType it(input,reg);
>        OutputIteratorType ot(output,reg);
>        for(it.GoToBegin();!it.IsAtEnd();++it){
>        ot.Set(it.Get());
>        ot++;
>        }
> }
>
>

You could do this easier with

A) The itkImageSliceIteratorWithIndex

or with

B)  The itkRegionOfInterestImageFilter



> so i wanted to cut out a 100x100 pieces beginning from (0,0) at each slice,
> and copy it to the output iterator
> visual studio will give me an error on the initialitaion of
> InputIteratorType it(input,reg);
> I couldnt find a way how to instantiate a 'null' InputIteraottype and fill
> if with the desired Region!
> is there a way like the above that i can adress slice-individually
> iterators?
>
>

Yes,

Use the

 The itkImageSliceIteratorWithIndex


http://www.itk.org/Doxygen/html/classitk_1_1ImageSliceConstIteratorWithIndex.html


Regards,


       Luis



> Thanks alot
> M
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