[Insight-users] problems computing similarity between images

[Petra Schneider]

Hello,

my intention is very simple. I need to compute the similarity between different
regions of two images using NormalizedCorrelationImageToImageMetric (see my
code below).
But there seems to be a mistake. In some cases, I get the optimal metric value,
if I compare different regions of the same image. What's wrong? Need help.....


Thanks,
	Petra




int main( int argc, char ** args )
{

	typedef unsigned char  pixel_value;
	static const unsigned int  image_dimension ( 2 );
	typedef itk :: Image < pixel_value, image_dimension > 	 image_type;

	image_type :: Pointer 	image_fixed ( image_type :: New() );
	image_type :: Pointer 	image_moving ( image_type :: New() );

	typedef itk :: ImageFileReader < image_type >	 reader_type;
	reader_type :: Pointer	reader_fixed ( reader_type :: New() );
	reader_type :: Pointer	reader_moving ( reader_type :: New() );


	reader_fixed -> SetFileName ( args[ 1 ] );
	image_fixed = reader_fixed -> GetOutput();
	image_fixed -> Update();

	reader_moving -> SetFileName ( args[ 2 ] );
	image_moving = reader_moving -> GetOutput();
	image_moving -> Update();


	typedef itk :: TranslationTransform < double, image_dimension >
transform_type;
	typedef itk :: LinearInterpolateImageFunction < image_type, double >
interpolator_type;
	typedef itk :: NormalizedCorrelationImageToImageMetric < image_type,
image_type >  metric_type;
	typedef itk :: ExtractImageFilter < image_type, image_type >
extractor_type;
	typedef transform_type :: ParametersType  parameters_type;


	transform_type :: Pointer transform ( transform_type :: New() );
	interpolator_type :: Pointer interpolator ( interpolator_type :: New()
);
	metric_type :: Pointer metric ( metric_type :: New() );
	extractor_type :: Pointer extractor ( extractor_type :: New() );
	parameters_type parameters ( transform -> GetNumberOfParameters() );


	for ( unsigned int i = 0; i < transform -> GetNumberOfParameters(); i++
)
	{
		parameters[ i ] = 0.0;
	}


	image_type :: RegionType region_moving;
	image_type :: RegionType region_fixed;
	image_type :: IndexType index_moving;
	image_type :: IndexType index_fixed;
	image_type :: SizeType size_moving;
	image_type :: SizeType size_fixed;


	index_moving[ 0 ] = 5;		index_moving[ 1 ] = 0;
	index_fixed[ 0 ] = 0;		index_fixed[ 1 ] = 0;
	size_moving[ 0 ] = 400;		size_moving[ 1 ] = 395;
	size_fixed[ 0 ] = 400;		size_fixed[ 1 ] = 395;


	region_moving.SetSize( size_moving );
	region_moving.SetIndex( index_moving );
	region_fixed.SetSize ( size_fixed );
	region_fixed.SetIndex ( index_fixed );


	extractor -> SetInput ( image_moving );
	extractor -> SetExtractionRegion( region_moving );
	extractor -> Update();
	const image_type :: Pointer moving ( extractor -> GetOutput() );
	moving -> Update();


	image_fixed -> SetRegions ( region_fixed );
	//image_fixed -> Allocate();


	metric -> SetFixedImage ( image_fixed );
	metric -> SetFixedImageRegion( image_fixed -> GetRequestedRegion() );
	metric -> SetMovingImage( moving );
	metric -> SetTransform ( transform );
	metric -> SetTransformParameters ( parameters );
	metric -> SetInterpolator ( interpolator );
	metric -> Initialize();


	cout << metric -> GetValue ( parameters ) << endl;

}