[vtkusers] segmentation fault with vtkImageData and vtkMetaImageReader

[Jérôme]

That's much clearer now!
If your reader and cast filter are not in the same place (focus),
the smart pointer has deleted the reader. Now it's sure. The simplest
work around (but not the fanciest/cutest) would be:

reader->Update( );
vtkImagedata* readerOutput = vtkImageData::SafeDownCast(
reader->GetOutputDataObject( 0, 0 ));
vtkImageData* myImage = vtkImageData::New( );
myImage->DeepCopy( readerOutput );

Then you can use myImage everywhere you want. Don't forget to Delete( ) it,
since it is not a SmartPointer but a simple New() allocation.

HTH
Jerome


2011/6/8 Laurent Mundeleer <laurent.mundeleer at uclouvain.be>

> Hi Jerome,
> Thank you for your answer.
>
> The problem is that the reader and the cast are not done at the same
> place so that's why I have a vtkImageData which is transmitted in
> another parts of the code.
> I use a vtkImageData to have some informations such as dimensions,
> center, etc and because we use other types so we have sometimes to
> translate from vtkImageData to another image type (custom image types or
> QImage for instance).
>
> I understand I break the pipeline doing this as I have :
> reader->imageData | break
> imageData->cast->mapper-> etc
> instead of : reader->cast->mapper-> etc
> But if I want to keep the pipeline complete, I have to transmit a
> vtkAlgorithm pointer which is less usable outside of vtk, and actually I
> don't need the beginning of the pipeline, I have enough with the
> vtkImageData.
>
> Actually if I delete the reader pointer I have the same problem, so that
> means using the setInput() method as I do involves somewhere a call to
> myVtkImageData->GetProducerPort() which is became null...
>
> That means also I guess I can't use the same reader to read a lot of
> vtkImageData for instance (which would solve my leak problem), because
> somewhere it keeps a reference to the reader which has done the import
> in the vtkImageData.
> I can't imagine what happen if I read a first vtkImageData, and then a
> second, and try to display or apply a filter to the first one.
>
> Thanks,
>
> Laurent
>
> On Wed, 2011-06-08 at 16:42 +0200, Jérôme wrote:
> > Hi,
> >
> > You should use cast->SetInputConnection( reader->GetOutputPort( ) );
> > instead of the old fashion SetInput.
> > IMHO, the problem is that your smart pointer, for some reasons
> > (reference count becomes null), decided to deallocate the reader, and
> > thus the underlying output.
> >
> > HTH,
> > Jerome
> >
> > 2011/6/7 Laurent Mundeleer <laurent.mundeleer at uclouvain.be>
> >         Hi everyone,
> >         I have a strange problem in reading a MetaImage.
> >         I have a segmentation fault when I access the vtkImageData,
> >         but if I use a direct pointer instead of a smartPointer on the
> >         vtkImageReader it's ok (but I have a memory leak).
> >
> >         What am I doing wrong ?
> >         Here are some code extracts of what is working :
> >
> >         // in reader method :
> >         ...
> >         vtkImageData *imageData = 0;
> >         ...
> >
> >         vtkMetaImageReader* reader = vtkMetaImageReader::New();
> >         //add to replace : vtkSmartPointer<vtkMetaImageReader> reader
> >         = vtkSmartPointer<vtkMetaImageReader>::New();
> >         // and have no delete at the end of the reading
> >         ..
> >         reader->Update();
> >         ...
> >         imageData = reader->GetOutput();
> >
> >         // no delete on the reader
> >
> >         /------------------------------------------
> >
> >         // in renderer method :
> >            vtkSmartPointer<vtkImageCast> castSource
> >         =vtkSmartPointer<vtkImageCast>::New();
> >            castSource->SetOutputScalarTypeToUnsignedChar();
> >            castSource->SetInput(imageData); // seg fault
> >            castSource->Update();
> >
> >         /---------------------------------------------
> >         // or in unit test :
> >         vtkImageData*volume = readingMethod();
> >         ...
> >         double *origin = volume->GetOrigin(); // seg fault
> >
> >
> >         Thank you for any help,
> >         Best Regards,
> >
> >         ++
> >         Laurent
> >
> >
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