[Insight-developers] [ITK + Python] Wrapping classes proposal

[Gaetan Lehmann]

On Tue, 14 Jun 2005 12:34:57 +0200, Benoit Regrain  
<benoit.regrain at creatis.insa-lyon.fr> wrote:


>> But if it's possible to add an attribute to the class which cleany  
>> identify the type (as you say below), we don't have to worry about name  
>> : we should just use the new attributes.
>> If names are not changed, we keep full compatibility with older itk  
>> versions...
> Yes, you have right in theory. And I understand the will to keep this
> compatibility. But I'm not sure that's easily possible.
>
> Consider the itk::Image < itk::Vector<float,2>, 2> with an attribute to
> get the mangled add.
> So, for the itk::Vector<float,2>, the attribute will have 'VF2'
> So, when we will search the type of the image, we will search 'VF22'
> But the wrapped image classes for the want type are 'VF2' or 'V2F2'
> and never 'VF22'
>
> So, I see only one solution. Create the _ItkClassXxx while wrapping
> and generate the link between a wanted 'VF22' and a real 'V2F2' or 'VF2'
> But I don't know if it's possible with CableSwig or Swig.
>
> In other hand, is it really a problem to not keep the backward  
> compatibility
> in all cases ?
> Actually, the known persons working with ITK (in the same society than  
> me)
> are afraid by the use of itk in python. But after a little sounding, it  
> appears that
> a change of the mangled names with a simplest use in the wrapped  
> languages
> will be more attractive.
> It's why I prefer a change of the mangled name (if we don't have other
> choice)

ok

>
>
>
>>>> But there is good and less good things in c++ style, and I find quite
>>>> boring
>>>> to have to set parameters on several lines, or to have to call
>>>> a.SetInput(b.GetOutput()) for each filter, especially in interperter.
>>>> So I have given the ability to set attribute value in New method :
>>>>
>>>>  reader = itk.ImageFileReader[imageType].New(FileName='image.png')
>>>>
>>>> and to make construction of the process pipeline easier, if a var is  
>>>> used
>>>> as
>>>> parameter in New method, it is used as source of image :
>>>>
>>>>  reader2 = itk.ImageFileReader[imageType].New(FileName='image2.png')
>>>>  sub = itk.SubtractImageFilter[imageType, imageType,
>>>> imageType].New(reader,
>>>> reader2)
>>>>  writer = itk.ImageFileWriter[imageType].New(sub, FileName='out.png')
>>>>  writer.Update()
>>>>
>>>> All of this make code short, readable and flexible.
>>> This can be a good addict. But some processes in ITK don't have the  
>>> SetInput
>>> method (reader processes for example). How does the function
>>> react in this case ? Does your solution work in all cases ?
>>
>> I use the SetInput(int, image) method, and if it fail (for  
>> itkImageToVTKImageFilter for example), I try with SetImage(image). If  
>> it still fail, it return a AttributeError, exactly as using SetInput if  
>> it does not exists.
>> I don't see case where it can't work...
> For me, it will stay in a second (interessant) point. At this time, I  
> focus on a
> best use of the itk wrapping (essentially with python).
>

I done like you when I began to write my module, but when I have seen that  
this module allow me to add feature which reduce amount of code, I haven't  
hesitate to add it.
I hope you will come to it soon ;-)

>
>>>> I agree that type names are not really consistent, but I'm not sure  
>>>> your
>>>> solution is totally doable. How would you call wrapped
>>>> BinaryDilateImageFilter :
>>>>
>>>>    ITK_WRAP_OBJECT3(BinaryDilateImageFilter, image::F2 , image::F2 ,
>>>> structuringElement::F2,   itkBinaryDilateImageFilterF2F2  );
>>>
>>> The images are : IF2
>>> For the structure element, we can prefix by SE, so we have the result  
>>> : SEF2
>>> Finally, we obtain : BinaryDilateUmageFilterIF2IF2SEF2
>>>
>>> But we may consider that the structure element can be different that
>>> structuringElement::F2
>>> for each 2D images process, so the resulting mangled name will be :
>>> BinaryDilateUmageFilterIF2IF2
>>
>> I thinkk your sentence is not ended :-)
> Are you sure ? :-( lol
>

So I should have miss something :-/

>
>
>
>>> I will see to have a mix between our solutions. But I think the first  
>>> point
>>> to solve is to have a coherence between all mangled names.
>>
>> If you can implement class creation at wrapping time, it would be  
>> really great : it's important for me to be able to use completion.
>> Also, I found usage of [type] (__getitem__) much nice than giving the  
>> type in New function, and it allow to use New for other things.
>> On the other side, your typing mechanism is stronger than mine (which  
>> is nothing more than refinding the string used in InsightToolkit  
>> module) and allow interesting things, such as the example you have  
>> given :-)
> I have finished to mix our 2 codes. The result is very good and offers a  
> simple use
> But with a first parse of the itk classes :-(
> I have used my parsing and adapted it to your classes. I have added some  
> usefull
> methods in classes to have facilities.

Great:-), but sadely you took an old version of my module, and lots of  
things are better now, without talking of New method facilities (dict  
interface for types, no names with _ prefix in itk module, better  
management of __call__ to be consistent with vtk, ...)
I'm modifying it to integrate changes.

Also, I don't really understand the can_instanciate method : some classes  
can be instanciated without New method, just with () (Ex: itk.Index[2]())

>
> In your solution, you have kept the _New, _Pointer, _SuperClass, etc.  
> extentions
> to create corresponding methods New, Pointer, SuperClass. What is the  
> interest
> to keep Pointer, Superclas, etc. ? Have the New method seems to me the  
> only
> usefull method.

I don't know if other methods are useful. In doubt, I kept them. The goal  
was to make everything in InsightToolkit module avaible in itk module.

>> Can we get your code somewhere ?
> Yes, I have made a CVS repository on our server :
>    CVSROOT : :pserver:anonymous at cvs.creatis.insa-lyon.fr:2402/cvs/public
>    No password or anonymous ... I never remember it

passwd: anonymous

>    Module name : itkWrapping
>
> All is in the python directory :
>  itkParser.py : the parser of the itk classes
>  itk.py : creation of classes
>  itkTestX.py : 3 tests presenting the use and limitations
>

-- 
Gaetan Lehmann <gaetan.lehmann at jouy.inra.fr>
Tel: +33 1 34 65 29 66
Biologie du Développement et de la Reproduction
INRA de Jouy-en-Josas (France)
Web: http://voxel.jouy.inra.fr