[Insight-users] Possible bug in GaussianSpatialObject

[Ali -]

Julien,

Thanks for trying this, the Update() of SpatialObjectToImageFilter 
method is called was called during the test. Could you give it a try 
with vtkImageWriter instead of vtkJPEGWriter  The minimal pipeline could 
produce the bug for Gaetan and I when it was ended with that filter.


-Ali

Julien Jomier wrote:
> Ali,
>
> I just tried adding ItkVtk and having vtkJPEGWriter at the end of the 
> pipeline and it works fine.
>
> Are you calling Update() explicitly on the SpatialObjectToImageFilter? 
> That might be the source of the problem.
>
> Julien
>
> Ali - wrote:
>> Julien,
>>
>> This seems to be one of those hard-to-detect bugs, now we know that it
>> is very unlikely that wrapping causes the problem. This is a minimal
>> pipeline which can generate the bug:
>>
>> [itk::GaussianSpatialObject] -> [itk::SpatialObjectToImageFilter] ->
>> [itkImageToVTKImageFilter] -> [vtkWriter]
>>
>> The reason that you have never encountered this problem in ITK is that
>> the pipelines normally end with an ITK writer. However, after passing
>> the image buffer to a VTK writer, the output file is broken.
>>
>> One may argue that this is an ItkVtkGlue bug, but the fact that we have
>> not observed anything similar in all other image filters suggests that
>> there is something different in SpatialObjectToImageFilter. Is it
>> possible that some, possibly optional, step is not performed in
>> SpatialObjectToImageFilter? If you can try this with ItkVtkGlue, it'd be
>> a big help to us.
>>
>>
>> -Ali
>>
>>
>> Julien Jomier wrote:
>> > Hi Ali,
>> >
>> > Couple of things:
>> >
>> > 1) Change the 
>> gaus.GetIndexToObjectTransform().SetTranslation(offset) to
>> > gaus.GetObjectToParentTransform().SetTranslation(offset)
>> >
>> > 2) Add gaus.ComputeObjectToWorldTransform(); after setting the
>> > translation. This forces the recomputation of the world transform for
>> > the object.
>> >
>> > 3) Don't forget to set the size of your image for the
>> > SpatialObjectToImageFilter using SetSize().
>> >
>> > Here's the code I've been using (C++ version)
>> >
>> > typedef itk::GaussianSpatialObject GSType;
>> > GSType::Pointer gsp = GSType::New();
>> >
>> > gsp->SetMaximum(255);
>> > gsp->SetRadius(7);
>> > typedef itk::Vector VectorType;
>> > VectorType v;
>> > v[0] = 10;
>> > v[1] = 10;
>> > gsp->GetObjectToParentTransform()->SetTranslation(v);
>> > gsp->ComputeObjectToWorldTransform();
>> >
>> > typedef itk::Image ImageType;
>> > typedef itk::SpatialObjectToImageFilter FilterType;
>> > FilterType::Pointer filter = FilterType::New();
>> > filter->SetInput(gsp);
>> > FilterType::SizeType size;
>> > size[0]=20;
>> > size[1]=20;
>> > filter->SetSize(size);
>> > filter->Update();
>> >
>> > typedef itk::ImageFileWriter WriterType;
>> > WriterType::Pointer writer= WriterType::New();
>> > writer->SetFileName("test.jpg");
>> > writer->SetInput(filter->GetOutput());
>> > writer->Update();
>> >
>> > Let me know if that works or not,
>> >
>> > Julien
>> >
>> > Ali - wrote:
>> >> Hi Julien,
>> >>
>> >> It seems there is this bug in GaussianSpatialObject which causes 
>> to mess
>> >> up the whole spatial object image when the translation transform is
>> >> applied. Here is an example:
>> >>
>> >> itkGaussianSpatialObject2 gaus = new itkGaussianSpatialObject2();
>> >> gaus.SetMaximum(255);
>> >> gaus.SetRadius(7);
>> >> itkVectorD2 offset = new itkVectorD2();
>> >> offset.SetElement(0, 0.0);
>> >> offset.SetElement(1, 0.0);
>> >> gaus.GetIndexToObjectTransform().SetTranslation(offset);
>> >>
>> >> (The above code is in java, but can be used as a pseudo code). 
>> Notice
>> >> that whether the offset is zero or not, setting the translation 
>> value
>> >> messes up the gaussian object. Here are the results:
>> >>
>> >> Without calling translation: http://i26.tinypic.com/2j4u7pd.jpg
>> >> With calling translation: http://i31.tinypic.com/iwrd5y.jpg
>> >>
>> >> All I wanted to do was to have a gaussian object at the centre of 
>> the
>> >> image. Is there a better way of doing this?
>> >>
>> >>
>> >> -Ali
>> >>
>> >>
>> >>
>> >>
>> >> 
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>



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