[Insight-developers] performance of image iterators and pixel buffer storage

[David Fuentes]

Dan, 
Thank you very much for the reply.

> See the documentation in itkImage.h:
>
> * The data in an image is arranged in a 1D array as [][][][slice][row][col]
> * with the column index varying most rapidly.  The Index type reverses
> * the order so that with Index[0] = col, Index[1] = row, Index[2] = slice,
> * ...
>
>> which value for
>>
>>  SetDirection()
>>
>> should be used to give the best performance?
>
> From my understanding, SetDirection(..) has no impact on iterator
> performance. SetDirection(..) changes the direction cosines, which are
> used by TransformPhysicalPointToIndex(..),
> TransformContinuousIndexToPhysicalPoint(..), and others in
> itk::OrientatedImage (although in ITK 3.10, which is about to be
> released, the direction cosines can be used in itk::Image, deprecating
> itk::OrientatedImage).
>


A little confused.
B/C of the memory storage setup, wouldn't you expect a significant cache
performance difference if you iterate over row's vs iterating over columns?
Are you saying that ITK iterators have some special abstraction to avoid
this?



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