# ChooseTextColorDemo

VTKExamples/Cxx/Visualization/ChooseTextColorDemo

### Code

ChooseTextColorDemo.cxx

    #include <vtkSmartPointer.h>

    #include <vtkBYUReader.h>
    #include <vtkOBJReader.h>
    #include <vtkPLYReader.h>
    #include <vtkPolyDataReader.h>
    #include <vtkSTLReader.h>
    #include <vtkXMLPolyDataReader.h>
    #include <vtkSphereSource.h>

    #include <vtkMath.h>
    #include <vtkCoordinate.h>
    #include <vtkTextProperty.h>
    #include <vtkTextActor.h>
    #include <vtkActor.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkCamera.h>

    #include <vtkNamedColors.h>

    #include <vtkNamedColors.h>
    namespace
    {
    // Given a color, find a contrasting color. If the goven color is "light",
    // use the lightColor otherwise use the darkColor
    void ChooseContrastingColor(double *rgbIn,
                                double *rgbOut,
                                double threshold = .5,
                                const std::string lightColor = "white",
                                const std::string darkColor = "black");
    }

    namespace
    {
    void ViewportBorder(vtkSmartPointer<vtkRenderer> &renderer,
                        double *color,
                        bool last = false);
    }
    int main (int argc, char *argv[])
    {
      vtkMath::RandomSeed(4355412); // for test result consistency

      double threshold = .5;
      std::string lightColor = "white";
      std::string darkColor = "black";
      if (argc > 1)
      {
        threshold = atof(argv[1]);
      }
      if (argc > 2)
      {
        lightColor = argv[2];
      }
      if (argc > 3)
      {
        darkColor = argv[3];
      }
      // Visualize
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      // Setup render window
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      std::vector<vtkSmartPointer<vtkRenderer>> renderers;
      unsigned int xGridDimensions = 10;
      unsigned int yGridDimensions = 10;
      for (int i = 0; i < static_cast<int>(xGridDimensions  * yGridDimensions); ++i)
      {
        // Create textActors
        vtkSmartPointer<vtkTextActor> textActor =
          vtkSmartPointer<vtkTextActor>::New();
        textActor->GetTextProperty()->SetJustificationToCentered();
        textActor->GetTextProperty()->SetVerticalJustificationToCentered();
        textActor->SetInput("Text");
        textActor->SetPosition(50, 50);
        textActor->GetTextProperty()->BoldOff();
        textActor->GetTextProperty()->SetFontSize(20);

        // Setup renderer
        vtkSmartPointer<vtkRenderer> renderer =
          vtkSmartPointer<vtkRenderer>::New();
        renderer->AddActor(textActor);;
        double hsv[3];
        hsv[0] = vtkMath::Random(0.0, 1.0);
        hsv[1] = vtkMath::Random(0.0, 1.0);
        hsv[2] = vtkMath::Random(0.0, 1.0);
        double rgb[3];
        vtkMath::HSVToRGB(hsv, rgb);
        renderer->SetBackground(rgb);
      // Compute a good color for text on the renderer background
      ChooseContrastingColor(renderer->GetBackground(),
                             rgb,
                             threshold,
                             lightColor,
                             darkColor);
      textActor->GetTextProperty()->SetColor(rgb);
        renderers.push_back(renderer);
        renderWindow->AddRenderer(renderer);
      }

      // Setup viewports for the renderers
      int rendererSize = 100;
      renderWindow->SetSize(
        rendererSize * xGridDimensions, rendererSize * yGridDimensions);
      for (int row = 0; row < static_cast<int>(yGridDimensions); row++)
      {
        for (int col = 0; col < static_cast<int>(xGridDimensions); col++)
        {
          int index = row * xGridDimensions + col;
          // (xmin, ymin, xmax, ymax)
          double viewport[4] = {
            static_cast<double>(col) * rendererSize /
            (xGridDimensions * rendererSize),
            static_cast<double>(yGridDimensions - (row + 1)) * rendererSize /
            (yGridDimensions * rendererSize),
            static_cast<double>(col + 1) * rendererSize /
            (xGridDimensions * rendererSize),
            static_cast<double>(yGridDimensions - row) * rendererSize /
            (yGridDimensions * rendererSize)};
          renderers[index]->SetViewport(viewport);
          ViewportBorder(renderers[index],
                         colors->GetColor3d("White").GetData(),
                         col == static_cast<int>(xGridDimensions));
        }
      }
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

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

      return EXIT_SUCCESS;
    }

    #include <vtkRenderer.h>
    #include <vtkPoints.h>
    #include <vtkCellArray.h>
    #include <vtkPolyData.h>
    #include <vtkPolyLine.h>
    #include <vtkPolyDataMapper2D.h>
    #include <vtkCoordinate.h>
    #include <vtkActor2D.h>
    #include <vtkProperty2D.h>
    namespace
    {
    // draw the borders of a renderer's viewport
    void ViewportBorder(vtkSmartPointer<vtkRenderer> &renderer,
                        double *color,
                        bool last)
    {
      // points start at upper right and proceed anti-clockwise
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();
      points->SetNumberOfPoints(4);
      points->InsertPoint(0, 1, 1, 0);
      points->InsertPoint(1, 0, 1, 0);
      points->InsertPoint(2, 0, 0, 0);
      points->InsertPoint(3, 1, 0, 0);

      // create cells, and lines
      vtkSmartPointer<vtkCellArray> cells =
        vtkSmartPointer<vtkCellArray>::New();
      cells->Initialize();

      vtkSmartPointer<vtkPolyLine> lines =
        vtkSmartPointer<vtkPolyLine>::New();

      // only draw last line if this is the last viewport
      // this prevents double vertical lines at right border
      // if different colors are used for each border, then do
      // not specify last
      if (last)
      {
        lines->GetPointIds()->SetNumberOfIds(5);
      }
      else
      {
      lines->GetPointIds()->SetNumberOfIds(4);
      }
      for(unsigned int i = 0; i < 4; ++i)
      {
        lines->GetPointIds()->SetId(i,i);
      }
      if (last)
      {
        lines->GetPointIds()->SetId(4, 0);
      }
      cells->InsertNextCell(lines);

      // now make tge polydata and display it
      vtkSmartPointer<vtkPolyData> poly =
        vtkSmartPointer<vtkPolyData>::New();
      poly->Initialize();
      poly->SetPoints(points);
      poly->SetLines(cells);

      // use normalized viewport coordinates since
      // they are independent of window size
      vtkSmartPointer<vtkCoordinate> coordinate =
        vtkSmartPointer<vtkCoordinate>::New();
      coordinate->SetCoordinateSystemToNormalizedViewport();

      vtkSmartPointer<vtkPolyDataMapper2D> mapper =
        vtkSmartPointer<vtkPolyDataMapper2D>::New();
      mapper->SetInputData(poly);
      mapper->SetTransformCoordinate(coordinate);

      vtkSmartPointer<vtkActor2D> actor =
        vtkSmartPointer<vtkActor2D>::New();
      actor->SetMapper(mapper);
      actor->GetProperty()->SetColor(color);
      // line width should be at least 2 to be visible at extremes

      actor->GetProperty()->SetLineWidth(4.0); // Line Width

      renderer->AddViewProp(actor);
    }
    }
    namespace
    {
    void ChooseContrastingColor(double *rgbIn,
                                double *rgbOut,
                                double threshold,
                                const std::string lightColor,
                                const std::string darkColor)
    {
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      double hsv[3];
      // If the value is <= .5, use a light color, otherwise use a dark color
      vtkMath::RGBToHSV(rgbIn, hsv);
      if (hsv[2] <= threshold)
      {
        colors->GetColor(lightColor.c_str(), rgbOut[0], rgbOut[1], rgbOut[2]);
      }
      else
      {
        colors->GetColor(darkColor.c_str(), rgbOut[0], rgbOut[1], rgbOut[2]);
      }
    }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ChooseTextColorDemo)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(ChooseTextColorDemo MACOSX_BUNDLE ChooseTextColorDemo.cxx )

    target_link_libraries(ChooseTextColorDemo ${VTK_LIBRARIES})

### Download and Build ChooseTextColorDemo

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

    cd ChooseTextColorDemo/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:

    ./ChooseTextColorDemo

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