ITK/Examples/ImageProcessing/ThresholdImageFilter

This example demonstrates how to threshold an image using a ThresholdImageFilter, which offers few different types of thresholds. The output shows the original image and the thresholded image.

ThresholdImageFilter.cxx

<source lang="cpp">

1. include "itkImage.h"
2. include "itkRescaleIntensityImageFilter.h"
3. include "itkThresholdImageFilter.h"
4. include <itkImageFileReader.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"

typedef itk::Image<unsigned char, 2> ImageType;

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

 if(argc < 2)
   {
   std::cerr << "Required: filename" << std::endl;
   return EXIT_FAILURE;
   }

 typedef itk::ImageFileReader<ImageType> ReaderType;
 ReaderType::Pointer reader = ReaderType::New();
 reader->SetFileName(argv[1]);
 reader->Update();

 typedef itk::ThresholdImageFilter <ImageType>
         ThresholdImageFilterType;

 ThresholdImageFilterType::Pointer thresholdFilter
         = ThresholdImageFilterType::New();
 thresholdFilter->SetInput(reader->GetOutput());
 thresholdFilter->ThresholdBelow(100);
 thresholdFilter->SetOutsideValue(0);
 thresholdFilter->Update();

 // Visualize first image
 typedef itk::ImageToVTKImageFilter<ImageType> ConnectorType;
 ConnectorType::Pointer originalConnector = ConnectorType::New();
 originalConnector->SetInput(reader->GetOutput());

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

 // Visualize padded image
 ConnectorType::Pointer thresholdedConnector = ConnectorType::New();
 thresholdedConnector->SetInput(thresholdFilter->GetOutput());

 vtkSmartPointer<vtkImageActor> thresholdedActor =
   vtkSmartPointer<vtkImageActor>::New();
 thresholdedActor->SetInput(thresholdedConnector->GetOutput());

 // There will be one render window
 vtkSmartPointer<vtkRenderWindow> renderWindow =
   vtkSmartPointer<vtkRenderWindow>::New();
 renderWindow->SetSize(600, 300);

 vtkSmartPointer<vtkRenderWindowInteractor> interactor =
   vtkSmartPointer<vtkRenderWindowInteractor>::New();
 interactor->SetRenderWindow(renderWindow);

 // 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<vtkRenderer> leftRenderer =
   vtkSmartPointer<vtkRenderer>::New();
 renderWindow->AddRenderer(leftRenderer);
 leftRenderer->SetViewport(leftViewport);
 leftRenderer->SetBackground(.6, .5, .4);

 vtkSmartPointer<vtkRenderer> rightRenderer =
   vtkSmartPointer<vtkRenderer>::New();
 renderWindow->AddRenderer(rightRenderer);
 rightRenderer->SetViewport(rightViewport);
 rightRenderer->SetBackground(.4, .5, .6);

 // Add the sphere to the left and the cube to the right
 leftRenderer->AddActor(originalActor);
 rightRenderer->AddActor(thresholdedActor);

 leftRenderer->ResetCamera();
 rightRenderer->ResetCamera();

 renderWindow->Render();

 vtkSmartPointer<vtkInteractorStyleImage> style =
   vtkSmartPointer<vtkInteractorStyleImage>::New();
 interactor->SetInteractorStyle(style);

 interactor->Start();

 return EXIT_SUCCESS;

}

</source>

CMakeLists.txt

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

PROJECT(ThresholdImageFilter)

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(ThresholdImageFilter ThresholdImageFilter.cxx) TARGET_LINK_LIBRARIES(ThresholdImageFilter vtkHybrid ITKBasicFilters ITKCommon ITKIO)

</source>