# ImageMapToColors

VTKExamples/Cxx/Images/ImageMapToColors

### Code

ImageMapToColors.cxx

    //
    // Displays a "grayscale" image as a full color image via the
    // vtkImageMapToColors filter, which uses a lookup table to
    // map scalar values to colors
    //
    #include <vtkImageActor.h>
    #include <vtkImageData.h>
    #include <vtkImageMapper3D.h>
    #include <vtkImageMapToColors.h>
    #include <vtkImageProperty.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkLookupTable.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSmartPointer.h>

    int main(int, char*[])
    {
      // Create a "grayscale" 16x16 image, 1-component pixels of type "double"
      vtkSmartPointer<vtkImageData> image =
        vtkSmartPointer<vtkImageData>::New();
      int imageExtent[6] = { 0, 15, 0, 15, 0, 0 };
      image->SetExtent(imageExtent);
      image->AllocateScalars(VTK_DOUBLE, 1);

      double scalarvalue = 0.0;

      for (int y = imageExtent[2]; y <= imageExtent[3]; y++)
      {
        for (int x = imageExtent[0]; x <= imageExtent[1]; x++)
        {
          double* pixel = static_cast<double*>(image->GetScalarPointer(x, y, 0));
          pixel[0] = scalarvalue;
          scalarvalue += 1.0;
        }
      }

      // Map the scalar values in the image to colors with a lookup table:
      vtkSmartPointer<vtkLookupTable> lookupTable =
        vtkSmartPointer<vtkLookupTable>::New();
      lookupTable->SetNumberOfTableValues(256);
      lookupTable->SetRange(0.0, 255.0);
      lookupTable->Build();

      // Pass the original image and the lookup table to a filter to create
      // a color image:
      vtkSmartPointer<vtkImageMapToColors> scalarValuesToColors =
        vtkSmartPointer<vtkImageMapToColors>::New();
      scalarValuesToColors->SetLookupTable(lookupTable);
      scalarValuesToColors->PassAlphaToOutputOn();
      scalarValuesToColors->SetInputData(image);

      // Create an image actor
      vtkSmartPointer<vtkImageActor> imageActor =
        vtkSmartPointer<vtkImageActor>::New();
      imageActor->GetMapper()->SetInputConnection(
        scalarValuesToColors->GetOutputPort());
      imageActor->GetProperty()->SetInterpolationTypeToNearest();

      // Visualize
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderer->AddActor(imageActor);
      renderer->ResetCamera();

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);

      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      vtkSmartPointer<vtkInteractorStyleImage> style =
        vtkSmartPointer<vtkInteractorStyleImage>::New();

      renderWindowInteractor->SetInteractorStyle(style);

      renderWindowInteractor->SetRenderWindow(renderWindow);
      renderWindow->Render();
      renderWindowInteractor->Initialize();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ImageMapToColors)

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

### Download and Build ImageMapToColors

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

    cd ImageMapToColors/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:

    ./ImageMapToColors

WINDOWS USERS

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