ImageThreshold

Description¶

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

Question

If you have a question about this example, please use the VTK Discourse Forum

Code¶

ImageThreshold.cxx

#include <vtkImageActor.h>
#include <vtkImageMandelbrotSource.h>
#include <vtkImageMapper3D.h>
#include <vtkImageThreshold.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  // Create an image.
  vtkNew<vtkImageMandelbrotSource> imageSource;
  imageSource->Update();

  vtkNew<vtkImageThreshold> imageThreshold;
  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.
  vtkNew<vtkImageActor> inputActor;
  inputActor->GetMapper()->SetInputConnection(imageSource->GetOutputPort());

  vtkNew<vtkImageActor> thresholdedActor;
  thresholdedActor->GetMapper()->SetInputConnection(
      imageThreshold->GetOutputPort());

  // There will be one render window.
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetSize(600, 300);
  renderWindow->SetWindowName("ImageThreshold");

  // And one interactor.
  vtkNew<vtkRenderWindowInteractor> interactor;
  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.
  vtkNew<vtkRenderer> leftRenderer;
  renderWindow->AddRenderer(leftRenderer);
  leftRenderer->SetViewport(leftViewport);
  leftRenderer->SetBackground(.6, .5, .4);
  leftRenderer->SetBackground(colors->GetColor3d("Sienna").GetData());

  vtkNew<vtkRenderer> rightRenderer;
  renderWindow->AddRenderer(rightRenderer);
  rightRenderer->SetViewport(rightViewport);
  rightRenderer->SetBackground(.4, .5, .6);
  rightRenderer->SetBackground(colors->GetColor3d("RoyalBlue").GetData());

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

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

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

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ImageThreshold)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  ImagingCore
  ImagingSources
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ImageThreshold: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(ImageThreshold MACOSX_BUNDLE ImageThreshold.cxx )
  target_link_libraries(ImageThreshold PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ImageThreshold
  MODULES ${VTK_LIBRARIES}
)

Download and Build ImageThreshold¶

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

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