[Insight-users] Can not reproduce metric value

[Quy Pham Sy]

hi, Thanks Bill, yes, i didnt think about it :"I tried, there is no
exception (in both cases i mentioned in my last post)

Quyps,


2009/10/5 Bill Lorensen <bill.lorensen at gmail.com>

> The difference could be that the internal values have higher precision
> than the printed values.
>
> You should be getting an exception with the try/catch.
>
>
> On Sun, Oct 4, 2009 at 1:51 PM, Quy Pham Sy <phamsyquybk at gmail.com> wrote:
> > hi,  Bill
> > Thanks very much for you help. I tried adding your code. Actually your
> code
> > outputs the metric value to screen, am i right?
> > To make all my question clearer
> > here is the summary, there're issues:
> >
> > 1 - When I used the output (final transform parameters) from
> > ImageRegistration7 example (in ITK source code)
> > to reproduce the metric  value directly from Metric Object (same as
> metric
> > object type used in ImageRegistration7 example)
> > I can not reproduce the same metric value as the example. Why?
> >
> > Output from ImageRegistration7
> > -------------------------------------
> >  Scale         = 1.08438
> >  Angle (radians) 0.154531
> >  Angle (degrees) 8.85397
> >  Center X      = 170.327
> >  Center Y      = 148.556
> >  Translation X = -26.6822
> >  Translation Y = -93.4428
> >  Iterations    = 500
> >  Metric value  = 4551.86
> > ---------------------------------------
> > Two input image: fixed.bmp; moving.bmp
> > Set params code for transformation of metric
> > ---------------------------------------------------
> > transform->SetScale(1.08438);
> > transform->SetAngle(0.154531);
> > TransformType::TranslationType translation;
> > translation[0] = -26.6822;
> > translation[1] = -93.6822;
> > transform->SetTranslation(translation);
> > MetricType::TransformParametersType transformParams =
> > transform->GetParameters();
> >
> > double metricval = metric->GetValue(transformParams);
> > /*result: metricval = 4570.285 still != 4551.86*/
> > ----------------------------------------------------
> >
> > 2. In theory,  the metric value from registration (determined by:
> transform
> > type, metric type, interpolate type) of two images (fixed image, moving
> > image) is supposed to be "MINIMUM METRIC VALUE".
> > But when i try a set of params (as following) i get a smaller value,
> event
> > down to 0 (still use two input image as above) the value which is
> impossible
> > since two images are not identical !!!
> > ----------------------------------------------
> > transform->SetScale(0.92632);
> > transform->SetAngle(0.15095);
> > TransformType::TranslationType translation;
> > translation[0] = 28.29828;
> > translation[1] = 94.07266;
> > transform->SetTranslation(translation);
> > MetricType::TransformParametersType transformParams =
> > transform->GetParameters();
> >
> > double metricval = metric->GetValue(transformParams);
> > /*result: metricval == 0 !!!! */
> > -------------------------------------------------
> > Really appreciate any suggest and help!
> >
> //========================================================================
> > //              HERE IS THE SOURCE CODE TO REPRODUCE THESE PROBLEMS
> >
> //========================================================================
> > int main( int argc, char * argv[] )
> > {
> > const     unsigned int   Dimension = 2;
> > typedef   unsigned char  PixelType;
> > typedef itk::Image< PixelType, Dimension >   ImageType;
> > typedef itk::ImageFileReader< ImageType >  ReaderType;
> > ReaderType::Pointer fixedReader  = ReaderType::New();
> > ReaderType::Pointer movingReader = ReaderType::New();
> >   fixedReader->SetFileName(  "fixed.bmp" );
> >   movingReader->SetFileName( "moving.bmp" );
> >
> > try
> > {
> > fixedReader->Update();
> > movingReader->Update();
> > }
> > catch( itk::ExceptionObject & excep )
> > {
> > std::cerr << "Exception catched !" << std::endl;
> > std::cerr << excep << std::endl;
> > }
> >
> > typedef itk::MeanSquaresImageToImageMetric< ImageType, ImageType >
> >  MetricType;
> > MetricType::Pointer metric = MetricType::New();
> > typedef itk::CenteredSimilarity2DTransform < double >  TransformType;
> > TransformType::Pointer transform = TransformType::New();
> > typedef itk::LinearInterpolateImageFunction< ImageType, double >
> >  InterpolatorType;
> > InterpolatorType::Pointer interpolator = InterpolatorType::New();
> > ImageType::Pointer fixedImage  = fixedReader->GetOutput();
> > ImageType::Pointer movingImage = movingReader->GetOutput();
> > typedef itk::CenteredTransformInitializer< TransformType, ImageType,
> > ImageType >  TransformInitializerType;
> > TransformInitializerType::Pointer initializer =
> > TransformInitializerType::New();
> > initializer->SetTransform(   transform );
> > initializer->SetFixedImage(  fixedImage );
> > initializer->SetMovingImage( movingImage );
> > initializer->MomentsOn();
> > initializer->InitializeTransform();
> > metric->SetTransform( transform );
> > metric->SetInterpolator( interpolator );
> > metric->SetFixedImage(  fixedImage  );
> > metric->SetMovingImage( movingImage );
> > metric->SetFixedImageRegion(  fixedImage->GetBufferedRegion()  );
> > try
> > {
> > metric->Initialize();
> > }
> > catch( itk::ExceptionObject & excep )
> > {
> > std::cerr << "Exception catched !" << std::endl;
> > std::cerr << excep << std::endl;
> > return EXIT_FAILURE;
> > }
> >
> //************************************************************************/
> >         //  CHANGE PARAMETERS HERE TO REPRODUCE PROBLEM
> > transform->SetScale(0.92632);
> > transform->SetAngle(0.15095);
> > TransformType::TranslationType translation;
> > translation[0] = 28.29828;
> > translation[1] = 94.07266;
> >
> >
> //*************************************************************************/
> >
> > transform->SetTranslation(translation);
> > MetricType::TransformParametersType transformParams =
> > transform->GetParameters();
> > double metricval = 0.0;
> > try
> > {
> > metricval = metric->GetValue(transformParams);
> > std::cout << "metricval: " << metricval << std::endl;
> > }
> > catch( itk::ExceptionObject & excep )
> > {
> > std::cerr << "Exception catched !" << std::endl;
> > std::cerr << excep << std::endl;
> > std::cout << "metricval: " << metricval << std::endl;
> > return EXIT_FAILURE;
> > }
> > return EXIT_SUCCESS;
> > }
> >
> =======================================================================================
> >
>
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