ITK/Examples/EdgesAndGradients/GradientMagnitudeRecursiveGaussianImageFilter

This example demonstrates how to compute the magnitude of the gradient of an image. The original image and its gradient magnitude are displayed on the screen.

GradientMagnitudeRecursiveGaussianImageFilter.cxx

<source lang="cpp">

1. include "itkImage.h"
2. include "itkImageFileReader.h"
3. include "itkImageFileWriter.h"
4. include "itkRescaleIntensityImageFilter.h"
5. include "itkGradientMagnitudeRecursiveGaussianImageFilter.h"

1. include <itkImageToVTKImageFilter.h>

1. include "vtkImageViewer.h"
2. include "vtkRenderWindowInteractor.h"
3. include "vtkSmartPointer.h"
4. include "vtkImageActor.h"
5. include "vtkInteractorStyleImage.h"
6. include "vtkRenderer.h"

int main(int argc, char * argv[]) {

 // Verify command line arguments
 if( argc < 2 )
   {
   std::cerr << "Usage: " << std::endl;
   std::cerr << argv[0] << "inputImageFile" << std::endl;
   return EXIT_FAILURE;
   }

 // Parse command line arguments
 std::string inputFilename = argv[1];

 // Setup types
 typedef itk::Image< float,  2 >   FloatImageType;
 typedef itk::Image< unsigned char, 2 >   UnsignedCharImageType;

 typedef itk::ImageFileReader< UnsignedCharImageType >  readerType;

 typedef itk::GradientMagnitudeRecursiveGaussianImageFilter<

UnsignedCharImageType, FloatImageType > filterType;

 // Create and setup a reader
 readerType::Pointer reader = readerType::New();
 reader->SetFileName( inputFilename.c_str() );

 // Create and setup a gradient filter
 filterType::Pointer gradientFilter = filterType::New();
 gradientFilter->SetInput( reader->GetOutput() );
 gradientFilter->Update();

 // To write the gradient image file, we must rescale the gradient values
 // to a reasonable range
 typedef itk::RescaleIntensityImageFilter<

FloatImageType, UnsignedCharImageType > rescaleFilterType;

 rescaleFilterType::Pointer rescaler = rescaleFilterType::New();
 rescaler->SetOutputMinimum(0);
 rescaler->SetOutputMaximum(255);
 rescaler->SetInput( gradientFilter->GetOutput() );
 rescaler->Update();

 typedef itk::ImageToVTKImageFilter<UnsignedCharImageType> ConnectorType;
 ConnectorType::Pointer originalConnector = ConnectorType::New();
 originalConnector->SetInput(reader->GetOutput());

 vtkSmartPointer<vtkImageActor> originalActor =
   vtkSmartPointer<vtkImageActor>::New();
 originalActor->SetInput(originalConnector->GetOutput());

 typedef itk::ImageToVTKImageFilter<UnsignedCharImageType> ConnectorType;
 ConnectorType::Pointer gradientMagnitudeConnector = ConnectorType::New();
 gradientMagnitudeConnector->SetInput(rescaler->GetOutput());

 vtkSmartPointer<vtkImageActor> gradientMagnitudeActor =
   vtkSmartPointer<vtkImageActor>::New();
 gradientMagnitudeActor->SetInput(gradientMagnitudeConnector->GetOutput());

 // Define viewport ranges
 // (xmin, ymin, xmax, ymax)
 double leftViewport[4] = {0.0, 0.0, 0.5, 1.0};
 double rightViewport[4] = {0.5, 0.0, 1.0, 1.0};

 // Setup both renderers
 vtkSmartPointer<vtkRenderWindow> renderWindow =
   vtkSmartPointer<vtkRenderWindow>::New();
 renderWindow->SetSize(600,300);

 vtkSmartPointer<vtkRenderer> leftRenderer =
   vtkSmartPointer<vtkRenderer>::New();
 renderWindow->AddRenderer(leftRenderer);
 leftRenderer->SetViewport(leftViewport);

 vtkSmartPointer<vtkRenderer> rightRenderer =
   vtkSmartPointer<vtkRenderer>::New();
 renderWindow->AddRenderer(rightRenderer);
 rightRenderer->SetViewport(rightViewport);

 leftRenderer->AddActor(originalActor);
 rightRenderer->AddActor(gradientMagnitudeActor);

 vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
   vtkSmartPointer<vtkRenderWindowInteractor>::New();
 vtkSmartPointer<vtkInteractorStyleImage> style =
   vtkSmartPointer<vtkInteractorStyleImage>::New();

 renderWindowInteractor->SetInteractorStyle(style);

 renderWindowInteractor->SetRenderWindow(renderWindow);
 renderWindowInteractor->Initialize();

 renderWindowInteractor->Start();

 return EXIT_SUCCESS;

} </source>

CMakeLists.txt

<source lang="cmake"> cmake_minimum_required(VERSION 2.6)

PROJECT(GradientMagnitudeRecursiveGaussianImageFilter)

include_directories(/home/doriad/src/ITK/Wrapping/WrapITK/ExternalProjects/ItkVtkGlue/src/)

FIND_PACKAGE(VTK REQUIRED) INCLUDE(${VTK_USE_FILE})

FIND_PACKAGE(ITK REQUIRED) INCLUDE(${ITK_USE_FILE})

ADD_EXECUTABLE(GradientMagnitudeRecursiveGaussianImageFilter GradientMagnitudeRecursiveGaussianImageFilter.cxx) TARGET_LINK_LIBRARIES(GradientMagnitudeRecursiveGaussianImageFilter vtkHybrid ITKBasicFilters ITKIO ITKCommon)

</source>