[Insight-developers] reinterpret_cast question

[Jisung Kim]

I will test the ImageAdaptor idea too. I think I have
to change the GetMeasurementVector method of
ImageToListAdaptor to return by value instead of by
reference.

Thanks,

--- Luis Ibanez <luis . ibanez at kitware . com> wrote:
> Hi Jisung,
> 
> The reinterpret_cast<.> may not be the best option
> for what you want to acomplish.
> 
> It may be safer to just use  ImageAdaptors.
> 
> You simply need to define a Pixel Accesor that
> will make your image of Scalars look as an image
> of Vectors.  (FixedArrays)
> 
> We already have an ImageAdaptor that makes the
> reverse operation: make an image of Vectors look
> like an image of scalars by selecting one of the
> vector components.
> 
> You may want to take a look at the
> 
>         itkNthElementPixelAccessor.h
> 
> The PixelAccessor you need is the reverse of this
> one.
> 
> Once you have defined a pixel Accessor, you can
> instantiate your ImageAdaptor on the fly, no need
> to create a specific class. Simply pass the
> PixelAccessor as template parameter.
> 
> 
> typedef itk::ImageAdaptor< ScalarImage,
> ScalarToVectorPixelAccessor >
>    myImageAdaptor;
> 
> myImageAdaptor::Pointer adaptor =
> myImageAdaptor::New();
> adaptor->SetImage(  scalarImage );
> 
> After this, the image adaptor behaves like an Image
> of
> vectors (or whatever type you defined in the
> PixelAccessor to
> be the output pixel type).
> 
> The final trick will be to verify that the
> Statistical framework
> is using Iterators that are "ImageAdaptor-friendly"
> 
> 
>      Luis
> 
> 
> ---------------------
> Jisung Kim wrote:
> 
> >Hi.
> >
> >I am doing an experiment with reinterpret_cast. The
> >purpose of the experiment is to see if
> >"reinterpret_cast"ing scalar pixel (int, chat,
> double)
> >to itk::FixedArray< PixelType, 1> works.
> >
> >I checked in the itkDummyImageToListAdaptorTest in
> >Testing/Code/Numerics/Statistics. The current
> >implementation of ImageToListAdaptor class accepts
> >only images with the pixel types of itk::FixedArray
> or
> >its derived classes( itk::Vector, itk::Point,
> >itk::RBGPixel...). Therefore, images with scalar
> >pixels have to be converted before using them with
> >ImageToListAdaptor class.
> >
> >In the new test program, I forced casting from
> scalar
> >pixel to itk::FixedArray< PixelType, 1>. And it
> worked
> >on all compilers. The casting works something like
> >this:
> >
> >typedef int ScalarPixelType ;
> >typedef itk::Image< ScalarPixelType, 3 >
> >ScalarImageType ;
> >typedef itk::FixedArrray< ScalarPixelType, 1 >
> >ArrayPixelType ;
> >
> >...... allocates and fills the scalar image ......
> >
> >ArrayPixelType& arrayPixel = 
> >*(reinterpret_cast< ArrayPixelType* >
> >             ( &(scalarImage->GetPixel(index) ) ) ;
> >
> >std::cout << arrayPixel[0] << std::endl ;
> >
> >I'm not familiar with the reinterpret_cast and
> >wondering if this is legitimate use of it.
> >
> >Any suggestions?
> >
> >Thanks,
> >
> >
> >=====
> >Jisung Kim
> >bahrahm at yahoo . com
> >106 Mason Farm Rd.
> >129 Radiology Research Lab., CB# 7515
> >Univ. of North Carolina at Chapel Hill
> >Chapel Hill, NC 27599-7515
> >
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> >
> >  
> >
> 
> 
> 
> 
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=====
Jisung Kim
bahrahm at yahoo . com
106 Mason Farm Rd.
129 Radiology Research Lab., CB# 7515
Univ. of North Carolina at Chapel Hill
Chapel Hill, NC 27599-7515

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