[Insight-users] Problem with resampling

[Luis Ibanez]

Hi Motes,

Depending on the optimizer that you are using,
the expression

   resampler->SetTransform( registration->GetTransform());

is incorrect, since not all optimizers set the Transform
to be the one holding the last registration parameters.

Please follow what the Examples do in

             Insight/Examples/Registration/


  transform->SetFixedParameters(
     registration->GetTransform()->GetFixedParameters() );

  OptimizerType::ParametersType finalParameters =
                    registration->GetLastTransformParameters();

  transform->SetParameters( finalParameters );

  resampler->SetTransform( transform );


BTW: looking at the differences between

  http://img718.imageshack.us/img718/5899/correct.jpg
  http://img203.imageshack.us/img203/8120/wrongd.jpg

It looks like both are oriented the same way, and that the
only difference is the intensity level that you are setting
in the Default value:

            resampler->SetDefaultPixelValue( 0 );

Is that black background what you consider to be incorrect ?



    Regards,


          Luis


-----------------------------------------------------
On Wed, Apr 21, 2010 at 8:00 AM, motes motes <mort.motes at gmail.com> wrote:

> Arg problem is still the same. I was previewing the moving image and
> not the registered image so any suggestions are still most welcome!
>
>
>
> On Wed, Apr 21, 2010 at 1:24 PM, motes motes <mort.motes at gmail.com> wrote:
> > After running an AffineTransform registration process I am trying to
> > compute the registered image using the following:
> >
> > // ....
> >    try {
> >      registration->Update();
> >    }
> >    catch( itk::ExceptionObject & err ) {
> >      std::cerr << "ExceptionObject caught !" << std::endl;
> >      std::cerr << err << std::endl;
> >      return;
> >    }
> >
> >    resampler->SetInput(imageM);
> >    resampler->SetInterpolator( registration->GetInterpolator() );
> >    resampler->SetTransform( registration->GetTransform());
> >    resampler->SetSize( imageF->GetLargestPossibleRegion().GetSize() );
> >    resampler->SetOutputSpacing( imageF->GetSpacing() );
> >    resampler->SetOutputOrigin( imageF->GetOrigin() );
> >    resampler->SetDefaultPixelValue( 0 );
> >    resampler->Update();
> >
> >    CopyImageToImage<typename FixedImageType::Pointer,
> > FixedImageType>(resampler->GetOutput(), imageR);
> >    display_image<FixedImageType, Volume, short>(imageR);
> >
> >
> > When I print the parameters after the registration I get:
> >
> > 25 = 1.06962 : [0.990631, 0.0905022, -0.0294116, -0.0802955, 1.00481,
> > -0.035022, 0.0491173, -0.00658597, 0.910021, -3.12388, 6.25156,
> > -21.9981]
> >
> > these I know are the correct parameters and should produce this image:
> >
> > http://img718.imageshack.us/img718/5899/correct.jpg
> >
> > after running the above resampler. But instead I get:
> >
> > http://img203.imageshack.us/img203/8120/wrongd.jpg
> >
> >
> > Any ideas on what might go wrong in the resampler, it looks like the
> > rotation is messed up for some reason?
> >
> > I have checked that the fixed and moving images are correct just
> > before running the resampler.
> >
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