[ITK] [ITK-users] Conversion of itk::Image to other formats

Lambert Zijp ljzijp at gmail.com
Fri Mar 11 09:42:21 EST 2016 

Including the source of ItkToAvs in the header solved the problem, thank
you!!

I tried to fool the compiler by calling the conversion function with 1
instead of 3:
rc = ItkToAvs<sPixelType, 1>(&pAvs, itkShortVolume);

The compiler however was not fooled:
*error C2664: 'ItkToAvs' : cannot convert parameter 2 from
'itk::SmartPointer<TObjectType>' to 'itk::SmartPointer<TObjectType>'*
*        with*
*        [*
*            TObjectType=itk::Image<sPixelType,3>*
*        ]*
*        and*
*        [*
*            TObjectType=itk::Image<sPixelType,1>*
*        ]*
*        No user-defined-conversion operator available that can perform
this conversion, or the operator cannot be called*

So the compiler *knows* what kind of image TObjectType is. Why does it
insist that you specify those parameters when it already knows them?

On Fri, Mar 11, 2016 at 2:38 PM, Timothee Evain <tevain at telecom-paristech.fr
> wrote:

> It seems to me that using extern with functions is redundant in C/C++
> since the compiler already treat functions as extern.
> So no need to put extern.
> Regarding the link error, I don't know, just ensure the part of the code
> where you use the function have access to the function (is it included ?).
> Also if you have split the declaration and the definition, remember that
> template need to see definition to do instanciation so you have to include
> the source in the header, or both in your main code.
>
> About the function figuring out the parameter, I'm not sure it's possible
> for the compiler to do template argument deduction from a templated
> template parameter.
> Someone with more knowledge about it should be able to help you more than
> I can.
>
> HTH,
>
> Tim
>
>
>
>
>
> ----- Mail original -----
> De: "Lambert Zijp" <ljzijp at gmail.com>
> À: "Timothee Evain" <tevain at telecom-paristech.fr>
> Cc: "Matt McCormick" <matt.mccormick at kitware.com>, insight-users at itk.org
> Envoyé: Vendredi 11 Mars 2016 13:14:06
> Objet: Re: [ITK] [ITK-users] Conversion of itk::Image to other formats
>
> Hi Timothee,
>
> Thank you for responding. That was the kind of help I hoped to get!
>
> Following code snippet compiles and links OK:
>
> *template<typename ValueType,unsigned int Dimension>*
> *int ItkToAvs(AVSfield** ppAvs, typename
> itk::Image<ValueType,Dimension>::Pointer InputImage)*
> *{ *
> *  return 0;*
> *}*
>
> *main()*
> *{*
> *  typedef   short sPixelType;*
> *  typedef itk::Image<sPixelType, 3> sVolume;*
>
> *  AVSfield  *pAvs = NULL;*
> *  sVolume::Pointer itkShortVolume;*
>
>
>
> *  rc = ItkToAvs<sPixelType, 3>(&pAvs, itkShortVolume);*
> *}*
>
> However, if I put that function in another file (included in the project of
> course) and add 'extern' before the 'int' return type, it compiles, but the
> linker complains with:
> *error LNK2019: unresolved external symbol "int __cdecl
> ItkToAvs<short,3>(struct AVSfield * *,class itk::SmartPointer<class
> itk::Image<short,3> >)*
> I am pretty sure that all code in that file is being linked because there
> are other functions in it that are used...
> Any idea what is going on?
>
> Also, it would be nice if the conversion function ItkToAvs could figure out
> what the pixeltype is and what the number of dimensions are, instead of
> providing them when calling the function. How can that be done?
>
> Greetings,
> Lambert
>
>
>
>
>
> On Fri, Mar 11, 2016 at 11:35 AM, Timothee Evain <
> tevain at telecom-paristech.fr> wrote:
>
> > Hello Lambert,
> >
> > Try something like this :
> >
> > template<typename ValueType,unsigned int Dimension>
> > extern int ItkToAvs(AVSfield** ppAvs, typename
> > itk::Image<ValueType,Dimension>::Pointer InputImage);
> >
> > This way you should be able to use the function for any itkImage type,
> > given that you provide the ValueType and the Dimension to the function at
> > compile time like :
> >
> > [...]=ItkToAvs<ValueType,Dimension>([...]);
> >
> > But I cannot guarantee that this is the best way to do it, since I'm
> quite
> > a beginner with templates.
> >
> > HTH,
> >
> > Tim
> >
> > ----- Mail original -----
> > De: "Lambert Zijp" <ljzijp at gmail.com>
> > À: "Matt McCormick" <matt.mccormick at kitware.com>
> > Cc: insight-users at itk.org
> > Envoyé: Jeudi 10 Mars 2016 18:06:35
> > Objet: Re: [ITK] [ITK-users] Conversion of itk::Image to other formats
> >
> > Hi Matt,
> >
> > Let me try it this way. I tried all the following prototypes, but none of
> > them worked. Probably some C++ syntax problem...
> >
> > template <class T1, int T2>
> > extern int ItkToAvs(AVSfield** ppAvs, itk::Image<T1, T2> pItkImage);
> >
> > template <int T2>
> > extern int ItkToAvs(AVSfield** ppAvs, itk::Image<fPixelType, T2>
> > pItkImage);
> >
> > extern int ItkToAvs(AVSfield** ppAvs, itk::Image<fPixelType, 3>
> pItkImage);
> >
> > template< typename TImage>
> > extern int ItkToAvs(AVSfield** ppAvs, TImage* pItkImage);
> >
> > template< typename TPixel, unsigned int VImageDimension>
> > extern int ItkToAvs(AVSfield** ppAvs, const itk::Image<TPixel,
> > VImageDimension> pItkImage);
> >
> > template< typename TObjectType>
> > extern int ItkToAvs(AVSfield** ppAvs, const
> itk::SmartPointer<TObjectType>
> > pItkImage);
> >
> > The first parameter is the output of the function. The second parameter
> is
> > any itk image.
> > As you can see, I don't know what I'm doing... Any idea what a good
> > prototype would be?
> >
> > Greetings,
> > Lambert
> >
> >
> > On Thu, Mar 10, 2016 at 5:40 PM, Matt McCormick <
> > matt.mccormick at kitware.com > wrote:
> >
> >
> > Hi Lambert,
> >
> > A function prototype without templates would be run-time to run-time
> > type comparison and conversion. The example shows how to do run-time
> > to compile-time comparison, and it is relevant to both in-memory and
> > file conversion.
> >
> > HTH,
> > Matt
> >
> > On Thu, Mar 10, 2016 at 11:28 AM, Lambert Zijp < ljzijp at gmail.com >
> wrote:
> > > Hi Sarthak,
> > > There is no file I/O involved. It is about conversion in memory. In my
> > > original post, MyFormat is a struct containing things like pixeltype
> and
> > > number of dimensions and a couple of pointers to the pixels, the sizes
> of
> > > the dimensions, and the coordinates. Conversion from MyFormat to itk, I
> > got
> > > more or less working. Now I want to convert from itk to MyFormat. A
> > function
> > > prototype is needed...
> > >
> > > Greetings,
> > > Lambert
> > >
> > > On Thu, Mar 10, 2016 at 5:02 PM, Scapegoat Sarthak
> > > < scapegoat.sarthak at gmail.com > wrote:
> > >>
> > >> Hi Lambert,
> > >>
> > >> What you could do is to make a function what just takes in a file name
> > as
> > >> input and call the templated ITK function inside as an inline
> function.
> > >> There is no way I know to do I/O in ITK without using templates.
> > >>
> > >> Best,
> > >> Sarthak
> > >>
> > >>
> > >> On 10 March 2016 at 10:55, Lambert Zijp < ljzijp at gmail.com > wrote:
> > >>>
> > >>> Hi Scapegoat,
> > >>> Thank you for responding. What would the function prototype then be
> (of
> > >>> function that accepts any itk image. I mean, the syntax, preferably
> not
> > >>> templated)?
> > >>> Because I deal mostly with 3D or 4D signed short pixels (medical
> > images),
> > >>> I keep them as they are: half the memory consumption and easier
> > histogram
> > >>> computations.
> > >>>
> > >>> Greetings,
> > >>> Lambert
> > >>>
> > >>> On Thu, Mar 10, 2016 at 4:35 PM, Scapegoat Sarthak
> > >>> < scapegoat.sarthak at gmail.com > wrote:
> > >>>>
> > >>>> I would advice you to perform a check on the image dimensions (2 or
> 3)
> > >>>> and keep the pixel type as float throughout. In any case you will be
> > doing
> > >>>> computation so the extra memory is going to be helpful.
> > >>>>
> > >>>>
> > >>>> On 10 March 2016 at 10:28, Matt McCormick <
> > matt.mccormick at kitware.com >
> > >>>> wrote:
> > >>>>>
> > >>>>> Hi Lambert,
> > >>>>>
> > >>>>> This example shows how to read in an unknown image type. It
> > >>>>> demonstrates how to go between run-time type specification and the
> > >>>>> compile-image type specification of ITK.
> > >>>>>
> > >>>>>
> > >>>>>
> >
> http://itk.org/ITKExamples/src/IO/ImageBase/ReadUnknownImageType/Documentation.html
> > >>>>>
> > >>>>> This approach could be used for your problem.
> > >>>>>
> > >>>>> HTH,
> > >>>>> Matt
> > >>>>>
> > >>>>> On Thu, Mar 10, 2016 at 9:56 AM, Lambert Zijp < ljzijp at gmail.com >
> > wrote:
> > >>>>> > Dear itk users,
> > >>>>> > I'm new to itk and also not very proficient in C++...
> > >>>>> > I want to try some deformable registration methods implemented in
> > >>>>> > itk, and
> > >>>>> > need to convert my own format of images and volumes to itk, and
> > back.
> > >>>>> > For conversion to itk, I use 'ImportImageFilter', because I do
> not
> > >>>>> > want to
> > >>>>> > make a copy of the pixels/voxels.
> > >>>>> > Converting itk images and volumes back to my own format, is
> giving
> > me
> > >>>>> > a
> > >>>>> > headache; I'm confused about 'Image', SmartPointer and
> ConstPointer
> > >>>>> > and
> > >>>>> > template stuff.
> > >>>>> > Could you get me started by suggesting me a function prototype?
> > >>>>> >
> > >>>>> > Something like:
> > >>>>> > int ItkToMyFormat(MyFormat** ppMyFormat, itk::Image* pItkImage);
> > >>>>> >
> > >>>>> > The ItkImage can be any pixeltype, any dimension, and vector
> images
> > >>>>> > should
> > >>>>> > also be accepted by the conversion routine. In that conversion
> > >>>>> > function, and
> > >>>>> > need to be able to put a switch on pixeltype and number of
> > >>>>> > dimensions.
> > >>>>> >
> > >>>>> > Greetings,
> > >>>>> > Lambert
> > >>>>> >
> > >>>>> > _____________________________________
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> >
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