[Insight-users] Plotting the metric

[Giorgos Pichis]

Dear all,

I am trying to check the metric (Mattes MI) values between two images, while
rotating the one over the other.
Therefore I use Euler2DTransform.
The results though of the plot aren't the expected.
I am comparing two test images where the one is rotated 10 degrees over the
other,
and the metric minimum is appeared in the value 1.
Do you know what might be the problem, or what should I change in the
following code?

Thanks a lot
Best Regards
Giorgos
........................................................................
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkMattesMutualInformationImageToImageMetric.h"
#include "itkEuler2DTransform.h"
#include "itkLinearInterpolateImageFunction.h"

int main( int argc, char * argv[] )
{
  if( argc < 3 )
    {
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0] << "  fixedImage  movingImage" << std::endl;
    return 1;
    }

  const     unsigned int   Dimension = 2;
  typedef   unsigned char  PixelType;
  typedef itk::Image< PixelType, Dimension >   ImageType;
  typedef itk::Image< PixelType, Dimension >   ImageType;
  typedef itk::ImageFileReader< ImageType >  ReaderType;

  ReaderType::Pointer fixedReader  = ReaderType::New();
  ReaderType::Pointer movingReader = ReaderType::New();

  fixedReader->SetFileName(  argv[ 1 ] );
  movingReader->SetFileName( argv[ 2 ] );

  try
    {
    fixedReader->Update();
    movingReader->Update();
    }
  catch( itk::ExceptionObject & excep )
    {
    std::cerr << "Exception catched !" << std::endl;
    std::cerr << excep << std::endl;
    }

  typedef itk::MattesMutualInformationImageToImageMetric< ImageType,
ImageType >  MetricType;
  MetricType::Pointer metric = MetricType::New();

  typedef itk::Euler2DTransform< double >  TransformType;
  TransformType::Pointer transform = TransformType::New();

  typedef itk::LinearInterpolateImageFunction<
                                 ImageType, double >  InterpolatorType;
  InterpolatorType::Pointer interpolator = InterpolatorType::New();

  metric->SetInterpolator( interpolator );
  metric->SetTransform( transform );

  metric->SetNumberOfHistogramBins( 20 );
  metric->SetNumberOfSpatialSamples( 10000 );

 transform->SetIdentity();

  ImageType::ConstPointer fixedImage  = fixedReader->GetOutput();
  ImageType::ConstPointer movingImage = movingReader->GetOutput();

  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 -1;
    }

      MetricType::TransformParametersType parameters(
transform->GetNumberOfParameters() );

      int RangeOfDegrees=50;
      double RangeInRadians=RangeOfDegrees * atan(1.0)/45.0;

      for (double i=-RangeInRadians; i<=RangeInRadians; i+=atan(1.0)/45.0)
      {
          parameters[0] = i;
          parameters[1] = 0;
          parameters[2] = 0;

          const double value = metric->GetValue( parameters );
          double finalAngleInDegrees = i * 45.0 / atan(1.0);
          std::cout << finalAngleInDegrees << "         "  << value <<
std::endl;
      }
  std::cout << std::endl;
  return 0;
}
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