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# LabelPlacementMapper

VTKEx/Cxx/Visualization/LabelPlacementMapper

### Description

This example demonstrates how to add labels from an array to points. Each point is given a priority that determines which labels are visible when space is limited.

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

LabelPlacementMapper.cxx

    #include <vtkActor.h>
    #include <vtkActor2D.h>
    #include <vtkIntArray.h>
    #include <vtkLabelPlacementMapper.h>
    #include <vtkPointData.h>
    #include <vtkPointSetToLabelHierarchy.h>
    #include <vtkPointSource.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSmartPointer.h>
    #include <vtkStringArray.h>

    int main(int, char *[])
    {
      // Create a point set.
      vtkSmartPointer<vtkPointSource> pointSource =
        vtkSmartPointer<vtkPointSource>::New();
      pointSource->SetNumberOfPoints(6);
      pointSource->Update();

      // Add label array.
      vtkSmartPointer<vtkStringArray> labels =
        vtkSmartPointer<vtkStringArray>::New();
      labels->SetNumberOfValues(6);
      labels->SetName("labels");
      labels->SetValue(0, "Priority 10");
      labels->SetValue(1, "Priority 7");
      labels->SetValue(2, "Priority 6");
      labels->SetValue(3, "Priority 4");
      labels->SetValue(4, "Priority 4");
      labels->SetValue(5, "Priority 4");
      pointSource->GetOutput()->GetPointData()->AddArray(labels);

      // Add priority array.
      vtkSmartPointer<vtkIntArray> sizes =
        vtkSmartPointer<vtkIntArray>::New();
      sizes->SetNumberOfValues(6);
      sizes->SetName("sizes");
      sizes->SetValue(0, 10);
      sizes->SetValue(1, 7);
      sizes->SetValue(2, 6);
      sizes->SetValue(3, 4);
      sizes->SetValue(4, 4);
      sizes->SetValue(5, 4);
      pointSource->GetOutput()->GetPointData()->AddArray(sizes);

      // Create a mapper and actor for the points.
      vtkSmartPointer<vtkPolyDataMapper> pointMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      pointMapper->SetInputConnection(pointSource->GetOutputPort());

      vtkSmartPointer<vtkActor> pointActor =
        vtkSmartPointer<vtkActor>::New();
      pointActor->SetMapper(pointMapper);

      // Generate the label hierarchy.
      vtkSmartPointer<vtkPointSetToLabelHierarchy> pointSetToLabelHierarchyFilter =
        vtkSmartPointer<vtkPointSetToLabelHierarchy>::New();
      pointSetToLabelHierarchyFilter->SetInputConnection(
        pointSource->GetOutputPort());
      pointSetToLabelHierarchyFilter->SetLabelArrayName("labels");
      pointSetToLabelHierarchyFilter->SetPriorityArrayName("sizes");
      pointSetToLabelHierarchyFilter->Update();

      // Create a mapper and actor for the labels.
      vtkSmartPointer<vtkLabelPlacementMapper> labelMapper =
        vtkSmartPointer<vtkLabelPlacementMapper>::New();
      labelMapper->SetInputConnection(
        pointSetToLabelHierarchyFilter->GetOutputPort());
      vtkSmartPointer<vtkActor2D> labelActor =
        vtkSmartPointer<vtkActor2D>::New();
      labelActor->SetMapper(labelMapper);

      // Create a renderer, render window, and interactor.
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      // Add the actors to the scene.
      renderer->AddActor(pointActor);
      renderer->AddActor(labelActor);

      // Render and interact.
      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(LabelPlacementMapper)

    find_package(VTK COMPONENTS
      vtkvtkCommonCore
      vtkvtkCommonDataModel
      vtkvtkFiltersSources
      vtkvtkInteractionStyle
      vtkvtkRenderingContextOpenGL2
      vtkvtkRenderingCore
      vtkvtkRenderingFreeType
      vtkvtkRenderingGL2PSOpenGL2
      vtkvtkRenderingLabel
      vtkvtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping LabelPlacementMapper: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(LabelPlacementMapper MACOSX_BUNDLE LabelPlacementMapper.cxx )
      target_link_libraries(LabelPlacementMapper PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(LabelPlacementMapper MACOSX_BUNDLE LabelPlacementMapper.cxx )
      target_link_libraries(LabelPlacementMapper PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS LabelPlacementMapper
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build LabelPlacementMapper

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

    cd LabelPlacementMapper/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:

    ./LabelPlacementMapper

WINDOWS USERS

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