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ImageRegistration5.cxx
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ImageRegistration5.cxx
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/*=========================================================================
*
* Copyright Insight Software Consortium
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
// Software Guide : BeginCommandLineArgs
// INPUTS: {BrainProtonDensitySliceBorder20.png}
// INPUTS: {BrainProtonDensitySliceRotated10.png}
// OUTPUTS: {ImageRegistration5Output.png}
// OUTPUTS: {ImageRegistration5DifferenceAfter.png}
// OUTPUTS: {ImageRegistration5DifferenceBefore.png}
// ARGUMENTS: 0.1
// Software Guide : EndCommandLineArgs
// Software Guide : BeginCommandLineArgs
// INPUTS: {BrainProtonDensitySliceBorder20.png}
// INPUTS: {BrainProtonDensitySliceR10X13Y17.png}
// OUTPUTS: {ImageRegistration5Output2.png}
// OUTPUTS: {ImageRegistration5DifferenceAfter2.png}
// OUTPUTS: {ImageRegistration5DifferenceBefore2.png}
// ARGUMENTS: 1.0
// Software Guide : EndCommandLineArgs
// Software Guide : BeginLatex
//
// This example illustrates the use of the \doxygen{CenteredRigid2DTransform}
// for performing rigid registration in $2D$. The example code is for the
// most part identical to that presented in Section
// \ref{sec:IntroductionImageRegistration}. The main difference is the use
// of the CenteredRigid2DTransform here instead of the
// \doxygen{TranslationTransform}.
//
// \index{itk::CenteredRigid2DTransform}
//
// Software Guide : EndLatex
#include "itkImageRegistrationMethod.h"
#include "itkMeanSquaresImageToImageMetric.h"
#include "itkRegularStepGradientDescentOptimizer.h"
// Software Guide : BeginLatex
//
// In addition to the headers included in previous examples, the
// following header must also be included.
//
// \index{itk::CenteredRigid2DTransform!header}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
#include "itkCenteredRigid2DTransform.h"
// Software Guide : EndCodeSnippet
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkResampleImageFilter.h"
#include "itkSubtractImageFilter.h"
#include "itkRescaleIntensityImageFilter.h"
// The following section of code implements a Command observer
// that will monitor the evolution of the registration process.
//
#include "itkCommand.h"
class CommandIterationUpdate : public itk::Command
{
public:
typedef CommandIterationUpdate Self;
typedef itk::Command Superclass;
typedef itk::SmartPointer<Self> Pointer;
itkNewMacro( Self );
protected:
CommandIterationUpdate() {};
public:
typedef itk::RegularStepGradientDescentOptimizer OptimizerType;
typedef const OptimizerType * OptimizerPointer;
void Execute(itk::Object *caller, const itk::EventObject & event)
{
Execute( (const itk::Object *)caller, event);
}
void Execute(const itk::Object * object, const itk::EventObject & event)
{
OptimizerPointer optimizer = static_cast< OptimizerPointer >( object );
if( ! itk::IterationEvent().CheckEvent( &event ) )
{
return;
}
std::cout << optimizer->GetCurrentIteration() << " ";
std::cout << optimizer->GetValue() << " ";
std::cout << optimizer->GetCurrentPosition() << std::endl;
}
};
int main( int argc, char *argv[] )
{
if( argc < 4 )
{
std::cerr << "Missing Parameters " << std::endl;
std::cerr << "Usage: " << argv[0];
std::cerr << " fixedImageFile movingImageFile ";
std::cerr << " outputImagefile [differenceAfterRegistration] ";
std::cerr << " [differenceBeforeRegistration] ";
std::cerr << " [initialStepLength] "<< std::endl;
return EXIT_FAILURE;
}
const unsigned int Dimension = 2;
typedef unsigned char PixelType;
typedef itk::Image< PixelType, Dimension > FixedImageType;
typedef itk::Image< PixelType, Dimension > MovingImageType;
// Software Guide : BeginLatex
//
// The transform type is instantiated using the code below. The only
// template parameter for this class is the representation type of the
// space coordinates.
//
// \index{itk::CenteredRigid2DTransform!Instantiation}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
typedef itk::CenteredRigid2DTransform< double > TransformType;
// Software Guide : EndCodeSnippet
typedef itk::RegularStepGradientDescentOptimizer OptimizerType;
typedef itk::MeanSquaresImageToImageMetric<
FixedImageType,
MovingImageType > MetricType;
typedef itk:: LinearInterpolateImageFunction<
MovingImageType,
double > InterpolatorType;
typedef itk::ImageRegistrationMethod<
FixedImageType,
MovingImageType > RegistrationType;
MetricType::Pointer metric = MetricType::New();
OptimizerType::Pointer optimizer = OptimizerType::New();
InterpolatorType::Pointer interpolator = InterpolatorType::New();
RegistrationType::Pointer registration = RegistrationType::New();
registration->SetMetric( metric );
registration->SetOptimizer( optimizer );
registration->SetInterpolator( interpolator );
// Software Guide : BeginLatex
//
// The transform object is constructed below and passed to the registration
// method.
//
// \index{itk::CenteredRigid2DTransform!New()}
// \index{itk::CenteredRigid2DTransform!Pointer}
// \index{itk::RegistrationMethod!SetTransform()}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
TransformType::Pointer transform = TransformType::New();
registration->SetTransform( transform );
// Software Guide : EndCodeSnippet
typedef itk::ImageFileReader< FixedImageType > FixedImageReaderType;
typedef itk::ImageFileReader< MovingImageType > MovingImageReaderType;
FixedImageReaderType::Pointer fixedImageReader = FixedImageReaderType::New();
MovingImageReaderType::Pointer movingImageReader = MovingImageReaderType::New();
fixedImageReader->SetFileName( argv[1] );
movingImageReader->SetFileName( argv[2] );
registration->SetFixedImage( fixedImageReader->GetOutput() );
registration->SetMovingImage( movingImageReader->GetOutput() );
fixedImageReader->Update();
registration->SetFixedImageRegion(
fixedImageReader->GetOutput()->GetBufferedRegion() );
// Software Guide : BeginLatex
//
// In this example, the input images are taken from readers. The code
// below updates the readers in order to ensure that the image parameters
// (size, origin and spacing) are valid when used to initialize the
// transform. We intend to use the center of the fixed image as the
// rotation center and then use the vector between the fixed image center
// and the moving image center as the initial translation to be applied
// after the rotation.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
fixedImageReader->Update();
movingImageReader->Update();
// Software Guide : EndCodeSnippet
typedef FixedImageType::SpacingType SpacingType;
typedef FixedImageType::PointType OriginType;
typedef FixedImageType::RegionType RegionType;
typedef FixedImageType::SizeType SizeType;
// Software Guide : BeginLatex
//
// The center of rotation is computed using the origin, size and spacing of
// the fixed image.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
FixedImageType::Pointer fixedImage = fixedImageReader->GetOutput();
const SpacingType fixedSpacing = fixedImage->GetSpacing();
const OriginType fixedOrigin = fixedImage->GetOrigin();
const RegionType fixedRegion = fixedImage->GetLargestPossibleRegion();
const SizeType fixedSize = fixedRegion.GetSize();
TransformType::InputPointType centerFixed;
centerFixed[0] = fixedOrigin[0] + fixedSpacing[0] * fixedSize[0] / 2.0;
centerFixed[1] = fixedOrigin[1] + fixedSpacing[1] * fixedSize[1] / 2.0;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The center of the moving image is computed in a similar way.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
MovingImageType::Pointer movingImage = movingImageReader->GetOutput();
const SpacingType movingSpacing = movingImage->GetSpacing();
const OriginType movingOrigin = movingImage->GetOrigin();
const RegionType movingRegion = movingImage->GetLargestPossibleRegion();
const SizeType movingSize = movingRegion.GetSize();
TransformType::InputPointType centerMoving;
centerMoving[0] = movingOrigin[0] + movingSpacing[0] * movingSize[0] / 2.0;
centerMoving[1] = movingOrigin[1] + movingSpacing[1] * movingSize[1] / 2.0;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The most straightforward method of initializing the transform parameters
// is to configure the transform and then get its parameters with the
// method \code{GetParameters()}. Here we initialize the transform by
// passing the center of the fixed image as the rotation center with the
// \code{SetCenter()} method. Then the translation is set as the vector
// relating the center of the moving image to the center of the fixed
// image. This last vector is passed with the method
// \code{SetTranslation()}.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
transform->SetCenter( centerFixed );
transform->SetTranslation( centerMoving - centerFixed );
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Let's finally initialize the rotation with a zero angle.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
transform->SetAngle( 0.0 );
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Now we pass the current transform's parameters as the initial
// parameters to be used when the registration process starts.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
registration->SetInitialTransformParameters( transform->GetParameters() );
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Keeping in mind that the scale of units in rotation and translation is
// quite different, we take advantage of the scaling functionality provided
// by the optimizers. We know that the first element of the parameters array
// corresponds to the angle that is measured in radians, while the other
// parameters correspond to translations that are measured in millimeters.
// For this reason we use small factors in the scales associated with
// translations and the coordinates of the rotation center .
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
typedef OptimizerType::ScalesType OptimizerScalesType;
OptimizerScalesType optimizerScales( transform->GetNumberOfParameters() );
const double translationScale = 1.0 / 1000.0;
optimizerScales[0] = 1.0;
optimizerScales[1] = translationScale;
optimizerScales[2] = translationScale;
optimizerScales[3] = translationScale;
optimizerScales[4] = translationScale;
optimizer->SetScales( optimizerScales );
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Next we set the normal parameters of the optimization method. In this
// case we are using an \doxygen{RegularStepGradientDescentOptimizer}.
// Below, we define the optimization parameters like the relaxation factor,
// initial step length, minimal step length and number of iterations. These
// last two act as stopping criteria for the optimization.
//
// \index{Regular\-Step\-Gradient\-Descent\-Optimizer!SetRelaxationFactor()}
// \index{Regular\-Step\-Gradient\-Descent\-Optimizer!SetMaximumStepLength()}
// \index{Regular\-Step\-Gradient\-Descent\-Optimizer!SetMinimumStepLength()}
// \index{Regular\-Step\-Gradient\-Descent\-Optimizer!SetNumberOfIterations()}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
double initialStepLength = 0.1;
// Software Guide : EndCodeSnippet
if( argc > 6 )
{
initialStepLength = atof( argv[6] );
}
// Software Guide : BeginCodeSnippet
optimizer->SetRelaxationFactor( 0.6 );
optimizer->SetMaximumStepLength( initialStepLength );
optimizer->SetMinimumStepLength( 0.001 );
optimizer->SetNumberOfIterations( 200 );
// Software Guide : EndCodeSnippet
// Create the Command observer and register it with the optimizer.
//
CommandIterationUpdate::Pointer observer = CommandIterationUpdate::New();
optimizer->AddObserver( itk::IterationEvent(), observer );
try
{
registration->Update();
std::cout << "Optimizer stop condition: "
<< registration->GetOptimizer()->GetStopConditionDescription()
<< std::endl;
}
catch( itk::ExceptionObject & err )
{
std::cerr << "ExceptionObject caught !" << std::endl;
std::cerr << err << std::endl;
return EXIT_FAILURE;
}
OptimizerType::ParametersType finalParameters =
registration->GetLastTransformParameters();
const double finalAngle = finalParameters[0];
const double finalRotationCenterX = finalParameters[1];
const double finalRotationCenterY = finalParameters[2];
const double finalTranslationX = finalParameters[3];
const double finalTranslationY = finalParameters[4];
const unsigned int numberOfIterations = optimizer->GetCurrentIteration();
const double bestValue = optimizer->GetValue();
// Print out results
//
const double finalAngleInDegrees = finalAngle * 180.0 / itk::Math::pi;
std::cout << "Result = " << std::endl;
std::cout << " Angle (radians) = " << finalAngle << std::endl;
std::cout << " Angle (degrees) = " << finalAngleInDegrees << std::endl;
std::cout << " Center X = " << finalRotationCenterX << std::endl;
std::cout << " Center Y = " << finalRotationCenterY << std::endl;
std::cout << " Translation X = " << finalTranslationX << std::endl;
std::cout << " Translation Y = " << finalTranslationY << std::endl;
std::cout << " Iterations = " << numberOfIterations << std::endl;
std::cout << " Metric value = " << bestValue << std::endl;
// Software Guide : BeginLatex
//
// Let's execute this example over two of the images provided in
// \code{Examples/Data}:
//
// \begin{itemize}
// \item \code{BrainProtonDensitySliceBorder20.png}
// \item \code{BrainProtonDensitySliceRotated10.png}
// \end{itemize}
//
// The second image is the result of intentionally rotating the first image
// by $10$ degrees around the geometrical center of the image. Both images
// have unit-spacing and are shown in Figure
// \ref{fig:FixedMovingImageRegistration5}. The registration takes $20$
// iterations and produces the results:
//
// \begin{center}
// \begin{verbatim}
// [0.177458, 110.489, 128.488, 0.0106296, 0.00194103]
// \end{verbatim}
// \end{center}
//
// These results are interpreted as
//
// \begin{itemize}
// \item Angle = $0.177458$ radians
// \item Center = $( 110.489 , 128.488 )$ millimeters
// \item Translation = $( 0.0106296, 0.00194103 )$ millimeters
// \end{itemize}
//
// As expected, these values match the misalignment intentionally introduced
// into the moving image quite well, since $10$ degrees is about $0.174532$
// radians.
//
// \begin{figure}
// \center
// \includegraphics[width=0.44\textwidth]{BrainProtonDensitySliceBorder20}
// \includegraphics[width=0.44\textwidth]{BrainProtonDensitySliceRotated10}
// \itkcaption[Rigid2D Registration input images]{Fixed and moving images
// are provided as input to the registration method using the CenteredRigid2D
// transform.}
// \label{fig:FixedMovingImageRegistration5}
// \end{figure}
//
//
// \begin{figure}
// \center
// \includegraphics[width=0.32\textwidth]{ImageRegistration5Output}
// \includegraphics[width=0.32\textwidth]{ImageRegistration5DifferenceBefore}
// \includegraphics[width=0.32\textwidth]{ImageRegistration5DifferenceAfter}
// \itkcaption[Rigid2D Registration output images]{Resampled moving image
// (left). Differences between the fixed and moving images, before (center)
// and after (right) registration using the CenteredRigid2D transform.}
// \label{fig:ImageRegistration5Outputs}
// \end{figure}
//
// Figure \ref{fig:ImageRegistration5Outputs} shows from left to right the
// resampled moving image after registration, the difference between fixed
// and moving images before registration, and the difference between fixed
// and resampled moving image after registration. It can be seen from the
// last difference image that the rotational component has been solved but
// that a small centering misalignment persists.
//
// \begin{figure}
// \center
// \includegraphics[height=0.32\textwidth]{ImageRegistration5TraceMetric1}
// \includegraphics[height=0.32\textwidth]{ImageRegistration5TraceAngle1}
// \includegraphics[height=0.32\textwidth]{ImageRegistration5TraceTranslations1}
// \itkcaption[Rigid2D Registration output plots]{Metric values, rotation
// angle and translations during registration with the CenteredRigid2D
// transform.}
// \label{fig:ImageRegistration5Plots}
// \end{figure}
//
// Figure \ref{fig:ImageRegistration5Plots} shows plots of the main output
// parameters produced from the registration process. This includes, the
// metric values at every iteration, the angle values at every iteration,
// and the translation components of the transform as the registration
// progress.
//
// Software Guide : EndLatex
typedef itk::ResampleImageFilter<
MovingImageType,
FixedImageType > ResampleFilterType;
TransformType::Pointer finalTransform = TransformType::New();
finalTransform->SetParameters( finalParameters );
finalTransform->SetFixedParameters( transform->GetFixedParameters() );
ResampleFilterType::Pointer resample = ResampleFilterType::New();
resample->SetTransform( finalTransform );
resample->SetInput( movingImageReader->GetOutput() );
resample->SetSize( fixedImage->GetLargestPossibleRegion().GetSize() );
resample->SetOutputOrigin( fixedImage->GetOrigin() );
resample->SetOutputSpacing( fixedImage->GetSpacing() );
resample->SetOutputDirection( fixedImage->GetDirection() );
resample->SetDefaultPixelValue( 100 );
typedef itk::ImageFileWriter< FixedImageType > WriterFixedType;
WriterFixedType::Pointer writer = WriterFixedType::New();
writer->SetFileName( argv[3] );
writer->SetInput( resample->GetOutput() );
try
{
writer->Update();
}
catch( itk::ExceptionObject & excp )
{
std::cerr << "ExceptionObject while writing the resampled image !" << std::endl;
std::cerr << excp << std::endl;
return EXIT_FAILURE;
}
typedef itk::Image< float, Dimension > DifferenceImageType;
typedef itk::SubtractImageFilter<
FixedImageType,
FixedImageType,
DifferenceImageType > DifferenceFilterType;
DifferenceFilterType::Pointer difference = DifferenceFilterType::New();
typedef unsigned char OutputPixelType;
typedef itk::Image< OutputPixelType, Dimension > OutputImageType;
typedef itk::RescaleIntensityImageFilter<
DifferenceImageType,
OutputImageType > RescalerType;
RescalerType::Pointer intensityRescaler = RescalerType::New();
intensityRescaler->SetOutputMinimum( 0 );
intensityRescaler->SetOutputMaximum( 255 );
difference->SetInput1( fixedImageReader->GetOutput() );
difference->SetInput2( resample->GetOutput() );
resample->SetDefaultPixelValue( 1 );
intensityRescaler->SetInput( difference->GetOutput() );
typedef itk::ImageFileWriter< OutputImageType > WriterType;
WriterType::Pointer writer2 = WriterType::New();
writer2->SetInput( intensityRescaler->GetOutput() );
try
{
// Compute the difference image between the
// fixed and moving image after registration.
if( argc > 4 )
{
writer2->SetFileName( argv[4] );
writer2->Update();
}
// Compute the difference image between the
// fixed and resampled moving image after registration.
TransformType::Pointer identityTransform = TransformType::New();
identityTransform->SetIdentity();
resample->SetTransform( identityTransform );
if( argc > 5 )
{
writer2->SetFileName( argv[5] );
writer2->Update();
}
}
catch( itk::ExceptionObject & excp )
{
std::cerr << "Error while writing difference images" << std::endl;
std::cerr << excp << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// Let's now consider the case in which rotations and translations are
// present in the initial registration, as in the following pair
// of images:
//
// \begin{itemize}
// \item \code{BrainProtonDensitySliceBorder20.png}
// \item \code{BrainProtonDensitySliceR10X13Y17.png}
// \end{itemize}
//
// The second image is the result of intentionally rotating the first image
// by $10$ degrees and then translating it $13mm$ in $X$ and $17mm$ in $Y$.
// Both images have unit-spacing and are shown in Figure
// \ref{fig:FixedMovingImageRegistration5b}. In order to accelerate
// convergence it is convenient to use a larger step length as shown here.
//
// \code{optimizer->SetMaximumStepLength( 1.0 );}
//
// The registration now takes $46$ iterations and produces the following
// results:
//
// \begin{center}
// \begin{verbatim}
// [0.174454, 110.361, 128.647, 12.977, 15.9761]
// \end{verbatim}
// \end{center}
//
// These parameters are interpreted as
//
// \begin{itemize}
// \item Angle = $0.174454$ radians
// \item Center = $( 110.361 , 128.647 )$ millimeters
// \item Translation = $( 12.977 , 15.9761 )$ millimeters
// \end{itemize}
//
// These values approximately match the initial misalignment intentionally
// introduced into the moving image, since $10$ degrees is about $0.174532$
// radians. The horizontal translation is well resolved while the vertical
// translation ends up being off by about one millimeter.
//
// \begin{figure}
// \center
// \includegraphics[width=0.44\textwidth]{BrainProtonDensitySliceBorder20}
// \includegraphics[width=0.44\textwidth]{BrainProtonDensitySliceR10X13Y17}
// \itkcaption[Rigid2D Registration input images]{Fixed and moving images
// provided as input to the registration method using the CenteredRigid2D
// transform.}
// \label{fig:FixedMovingImageRegistration5b}
// \end{figure}
//
//
// \begin{figure}
// \center
// \includegraphics[width=0.32\textwidth]{ImageRegistration5Output2}
// \includegraphics[width=0.32\textwidth]{ImageRegistration5DifferenceBefore2}
// \includegraphics[width=0.32\textwidth]{ImageRegistration5DifferenceAfter2}
// \itkcaption[Rigid2D Registration output images]{Resampled moving image
// (left). Differences between the fixed and moving images, before (center)
// and after (right) registration with the CenteredRigid2D transform.}
// \label{fig:ImageRegistration5Outputs2}
// \end{figure}
//
// Figure \ref{fig:ImageRegistration5Outputs2} shows the output of the
// registration. The rightmost image of this figure shows the difference
// between the fixed image and the resampled moving image after registration.
//
// \begin{figure}
// \center
// \includegraphics[height=0.32\textwidth]{ImageRegistration5TraceMetric2}
// \includegraphics[height=0.32\textwidth]{ImageRegistration5TraceAngle2}
// \includegraphics[height=0.32\textwidth]{ImageRegistration5TraceTranslations2}
// \itkcaption[Rigid2D Registration output plots]{Metric values, rotation
// angle and translations during the registration using the CenteredRigid2D
// transform on an image with rotation and translation mis-registration.}
// \label{fig:ImageRegistration5Plots2}
// \end{figure}
//
// Figure \ref{fig:ImageRegistration5Plots2} shows plots of the main output
// registration parameters when the rotation and translations are combined.
// These results include, the metric values at every iteration, the angle
// values at every iteration, and the translation components of the
// registration as the registration converges. It can be seen from the
// smoothness of these plots that a larger step length could have been
// supported easily by the optimizer. You may want to modify this value in
// order to get a better idea of how to tune the parameters.
//
// Software Guide : EndLatex
return EXIT_SUCCESS;
}