[Insight-users] Possible bug in GaussianSpatialObject

[Julien Jomier]

Ali,

The vtkImageWriter is a superclass for the other file formats, I don't 
know what you want me to try.

Julien

Ali - wrote:
> 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<2> 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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