# ImageAccumulateGreyscale

VTKExamples/Cxx/Images/ImageAccumulateGreyscale

### Code

ImageAccumulateGreyscale.cxx

    #include <vtkSmartPointer.h>

    #include <vtkImageReader2Factory.h>
    #include <vtkImageReader2.h>
    #include <vtkActor.h>
    #include <vtkBarChartActor.h>
    #include <vtkFieldData.h>
    #include <vtkImageAccumulate.h>
    #include <vtkImageData.h>
    #include <vtkImageExtractComponents.h>
    #include <vtkIntArray.h>
    #include <vtkLegendBoxActor.h>
    #include <vtkProperty2D.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkImageMagnitude.h>
    #include <vtkNamedColors.h>

    int main( int argc, char *argv[] )
    {
      // Handle the arguments
      if( argc < 2 )
      {
        std::cout << "Required arguments: filename" << std::endl;
        return EXIT_FAILURE;
      }

      vtkSmartPointer<vtkImageReader2Factory> readerFactory =
        vtkSmartPointer<vtkImageReader2Factory>::New();
      vtkSmartPointer<vtkImageReader2> reader =
        readerFactory->CreateImageReader2(argv[1]);
      reader->SetFileName(argv[1]);

      vtkSmartPointer<vtkImageMagnitude> magnitude =
        vtkSmartPointer<vtkImageMagnitude>::New();
      magnitude->SetInputConnection(reader->GetOutputPort());

      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      vtkSmartPointer<vtkIntArray> frequencies =
        vtkSmartPointer<vtkIntArray>::New();

      vtkSmartPointer<vtkImageAccumulate> histogram =
        vtkSmartPointer<vtkImageAccumulate>::New();
      histogram->SetInputConnection(magnitude->GetOutputPort());
      histogram->SetComponentExtent(0,255,0,0,0,0);
      histogram->SetComponentOrigin(0,0,0);
      histogram->SetComponentSpacing(1,0,0);
      histogram->IgnoreZeroOn();
      histogram->Update();

      int numberOfTuples = 64;
      frequencies->SetNumberOfComponents(1);
      frequencies->SetNumberOfTuples(numberOfTuples);
      vtkIdType* output = static_cast<vtkIdType*>(histogram->GetOutput()->GetScalarPointer());

      for(int j = 0; j < numberOfTuples; ++j)
      {
        frequencies->SetTuple1(j, *output++);
      }

      vtkSmartPointer<vtkDataObject> dataObject =
        vtkSmartPointer<vtkDataObject>::New();

      dataObject->GetFieldData()->AddArray( frequencies );

      // Create a vtkBarChartActor
      vtkSmartPointer<vtkBarChartActor> barChart =
        vtkSmartPointer<vtkBarChartActor>::New();

      barChart->SetInput(dataObject);
      barChart->SetTitle("Histogram");
      barChart->GetPositionCoordinate()->SetValue(0.1,0.05,0.0);
      barChart->GetPosition2Coordinate()->SetValue(0.95,0.85,0.0);
      barChart->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
      barChart->GetLegendActor()->SetNumberOfEntries(
        dataObject->GetFieldData()->GetArray(0)->GetNumberOfTuples());
      barChart->LegendVisibilityOff();
      barChart->LabelVisibilityOff();

      int count = 0;
      for(int i = 0; i < numberOfTuples; ++i)
      {
        barChart->SetBarColor( count++, colors->GetColor3d("Tomato").GetData());
      }

      // Visualize the histogram
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderer->AddActor(barChart);
      renderer->SetBackground(colors->GetColor3d("Peacock").GetData());
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      renderWindow->SetSize(640, 480);

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

      // Initialize the event loop and then start it
      renderWindow->Render();
      interactor->Initialize();
      interactor->Start();

      return  EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ImageAccumulateGreyscale)

    find_package(VTK COMPONENTS
      vtkCommonColor
      vtkCommonCore
      vtkCommonDataModel
      vtkIOImage
      vtkImagingCore
      vtkImagingMath
      vtkImagingStatistics
      vtkInteractionStyle
      vtkRenderingAnnotation
      vtkRenderingContextOpenGL2
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingGL2PSOpenGL2
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ImageAccumulateGreyscale: ${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(ImageAccumulateGreyscale MACOSX_BUNDLE ImageAccumulateGreyscale.cxx )
      target_link_libraries(ImageAccumulateGreyscale PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ImageAccumulateGreyscale MACOSX_BUNDLE ImageAccumulateGreyscale.cxx )
      target_link_libraries(ImageAccumulateGreyscale PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ImageAccumulateGreyscale
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ImageAccumulateGreyscale

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

    cd ImageAccumulateGreyscale/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:

    ./ImageAccumulateGreyscale

WINDOWS USERS

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