# ImageThreshold

VTKExamples/Cxx/Images/ImageThreshold

### Description

The image on the left is the input image and the image on the right is the thresholded version.

### Code

ImageThreshold.cxx

    #include <vtkSmartPointer.h>
    #include <vtkImageData.h>
    #include <vtkImageThreshold.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkRenderer.h>
    #include <vtkImageMapper3D.h>
    #include <vtkImageActor.h>
    #include <vtkImageCast.h>
    #include <vtkImageMandelbrotSource.h>

    int main(int, char *[])
    {
      // Create an image
      vtkSmartPointer<vtkImageMandelbrotSource> imageSource =
        vtkSmartPointer<vtkImageMandelbrotSource>::New();
      imageSource->Update();

      vtkSmartPointer<vtkImageThreshold> imageThreshold =
        vtkSmartPointer<vtkImageThreshold>::New();
      imageThreshold->SetInputConnection(imageSource->GetOutputPort());
      unsigned char lower = 100;
      unsigned char upper = 200;

      imageThreshold->ThresholdBetween(lower, upper);
      imageThreshold->ReplaceInOn();
      imageThreshold->SetInValue(255);
      imageThreshold->Update();

      // Create actors
      vtkSmartPointer<vtkImageActor> inputActor =
        vtkSmartPointer<vtkImageActor>::New();
      inputActor->GetMapper()->SetInputConnection(
        imageSource->GetOutputPort());

      vtkSmartPointer<vtkImageActor> thresholdedActor =
        vtkSmartPointer<vtkImageActor>::New();
      thresholdedActor->GetMapper()->SetInputConnection(
        imageThreshold->GetOutputPort());

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

      // And one interactor
      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);

      leftRenderer->AddActor(inputActor);
      rightRenderer->AddActor(thresholdedActor);

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

      renderWindow->Render();
      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ImageThreshold)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(ImageThreshold MACOSX_BUNDLE ImageThreshold.cxx )

    target_link_libraries(ImageThreshold ${VTK_LIBRARIES})

### Download and Build ImageThreshold

Danger

The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.

Click here to download ImageThreshold and its CMakeLists.txt file. Once the tarball ImageThreshold.tar has been downloaded and extracted,

    cd ImageThreshold/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

    cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

    make

and run it:

    ./ImageThreshold

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.