# ImageAccumulate

VTKExamples/Cxx/Images/ImageAccumulate

### Code

ImageAccumulate.cxx

    /*
     * In this example, the resulting histogram has 6 pixels (all of them) in the 3rd bin (value = 2) and zero in the rest of the bins
     */
    #include <vtkImageAccumulate.h>
    #include <vtkImageData.h>
    #include <vtkSmartPointer.h>

    static void CreateImage(vtkSmartPointer<vtkImageData> image);

    int main(int, char *[] )
    {
      vtkSmartPointer<vtkImageData> image = vtkSmartPointer<vtkImageData>::New();
      CreateImage(image);

      vtkSmartPointer<vtkImageAccumulate> imageAccumulate =
        vtkSmartPointer<vtkImageAccumulate>::New();
      imageAccumulate->SetInputData(image);
      imageAccumulate->SetComponentExtent(0,255,0,0,0,0);
      imageAccumulate->SetComponentOrigin(0,0,0);
      imageAccumulate->SetComponentSpacing(1,0,0); // This will count exactly the number of pixels of each color. Use (10,0,0) to make bins of width 10 instead.
      imageAccumulate->Update();

      int dims[3];
      imageAccumulate->GetOutput()->GetDimensions(dims);
      for(vtkIdType bin = 0; bin < dims[0]; ++bin)
      {
       std::cout << *(static_cast<int*>(imageAccumulate->GetOutput()->GetScalarPointer(bin, 0, 0))) << " ";
      }

      std::cout << std::endl;

      double mean[3];
      imageAccumulate->GetMean(mean);
      std::cout << "Mean: " << mean[0] << " " << mean[1] << " " << mean[2] << std::endl;

      return  EXIT_SUCCESS;
    }

    void CreateImage(vtkSmartPointer<vtkImageData> image)
    {
      // Specify the size of the image data
      image->SetDimensions(2,3,1);
      //image->SetExtent(0,2,0,3,0,1);
      image->AllocateScalars(VTK_DOUBLE,1);

      int* dims = image->GetDimensions();
      // int dims[3]; // can't do this

      std::cout << "Dims: " << " x: " << dims[0] << " y: " << dims[1] << " z: " << dims[2] << std::endl;

      // Fill every entry of the image data with "2.0"
      for (int z = 0; z < dims[2]; z++)
      {
        for (int y = 0; y < dims[1]; y++)
        {
          for (int x = 0; x < dims[0]; x++)
          {
            double* pixel = static_cast<double*>(image->GetScalarPointer(x,y,z));
            pixel[0] = 2.0;
          }
        }
      }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ImageAccumulate)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkImagingStatistics QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ImageAccumulate: ${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(ImageAccumulate MACOSX_BUNDLE ImageAccumulate.cxx )
      target_link_libraries(ImageAccumulate PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ImageAccumulate MACOSX_BUNDLE ImageAccumulate.cxx )
      target_link_libraries(ImageAccumulate PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ImageAccumulate
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ImageAccumulate

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

    cd ImageAccumulate/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:

    ./ImageAccumulate

WINDOWS USERS

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