# Screenshot

VTKExamples/Java/Utilities/Screenshot

### Description

vtkWindowToImageFilter object provides methods needed to read the data in a vtkWindow and use it as input to the imaging pipeline.

This is useful for saving an image to a file for example. The window can be read as either RGB or RGBA pixels

Other Languages

See (Cxx), (Python)

### Code

Screenshot.java

    import vtk.vtkActor;
    import vtk.vtkNamedColors;
    import vtk.vtkNativeLibrary;
    import vtk.vtkPolyDataMapper;
    import vtk.vtkRenderWindow;
    import vtk.vtkRenderWindowInteractor;
    import vtk.vtkRenderer;
    import vtk.vtkSphereSource;
    import vtk.vtkPNGWriter;
    import vtk.vtkWindowToImageFilter;

    public class Screenshot
    {
      // -----------------------------------------------------------------
      // Load VTK library and print which library was not properly loaded
      static
      {
        if (!vtkNativeLibrary.LoadAllNativeLibraries())
        {
          for (vtkNativeLibrary lib : vtkNativeLibrary.values())
          {
            if (!lib.IsLoaded())
            {
              System.out.println(lib.GetLibraryName() + " not loaded");
            }
          }
        }
        vtkNativeLibrary.DisableOutputWindow(null);
      }
      // -----------------------------------------------------------------

      public static void writeImage(vtkRenderWindow renWin, String fn)
      {
        vtkWindowToImageFilter windowToImageFilter = new vtkWindowToImageFilter();
        windowToImageFilter.SetInput(renWin);
        windowToImageFilter.SetScale(1);
        windowToImageFilter.SetInputBufferTypeToRGB();

        windowToImageFilter.ReadFrontBufferOff();
        windowToImageFilter.Update();

        vtkPNGWriter writer = new vtkPNGWriter();
        writer.SetFileName(fn);
        writer.SetInputConnection(windowToImageFilter.GetOutputPort());
        writer.Write();
      }

      public static void main(String args[])
      {
        //parse command line arguments
        if (args.length != 1)
        {
          System.err.println("Usage: java -classpath ... Filename(.png) e.g screenshot.png");
          return;
        }
        String fileName = args[0];

        vtkNamedColors colors = new vtkNamedColors();

        //Renderer Background Color
        double Bgcolor[] = new double[4];

        colors.GetColor("White", Bgcolor);

        vtkSphereSource sphereSource = new vtkSphereSource();
        sphereSource.SetCenter(0.0, 0.0, 0.0 );
        sphereSource.SetRadius(4.0);
        sphereSource.Update();

        vtkPolyDataMapper sphereMapper  = new vtkPolyDataMapper();
        sphereMapper.SetInputData (sphereSource.GetOutput());

        vtkActor sphereActor = new vtkActor();
        sphereActor.SetMapper(sphereMapper);

        // Create the renderer, render window and interactor.
        vtkRenderer ren = new vtkRenderer();
        vtkRenderWindow renWin = new vtkRenderWindow();
        renWin.AddRenderer(ren);
        renWin.SetAlphaBitPlanes(1);
        vtkRenderWindowInteractor iren = new vtkRenderWindowInteractor();
        iren.SetRenderWindow(renWin);

        // Visualise
        ren.AddActor(sphereActor);
        ren.SetBackground(Bgcolor);

        renWin.SetSize(300, 300);
        renWin.Render();

        writeImage(renWin, fileName);

        iren.Initialize();
        iren.Start();
      }
    }