# Screenshot

VTKExamples/Cxx/Utilities/Screenshot

### Description

This example shows how to save the window to a file (png in this case). You can combine this with the KeypressEvents example to make a useful functionality.

### Code

Screenshot.cxx

    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkSmartPointer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkPolyData.h>
    #include <vtkSphereSource.h>
    #include <vtkWindowToImageFilter.h>
    #include <vtkPNGWriter.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetCenter(0.0, 0.0, 0.0);
      sphereSource->SetRadius(5.0);
      sphereSource->Update();

      // Visualize
      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(sphereSource->GetOutputPort());

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);

      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      renderWindow->SetAlphaBitPlanes(1); //enable usage of alpha channel

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

      renderer->AddActor(actor);
      renderer->SetBackground(1,1,1); // Background color white

      renderWindow->Render();

      // Screenshot
      vtkSmartPointer<vtkWindowToImageFilter> windowToImageFilter =
        vtkSmartPointer<vtkWindowToImageFilter>::New();
      windowToImageFilter->SetInput(renderWindow);
      windowToImageFilter->SetMagnification(3); //set the resolution of the output image (3 times the current resolution of vtk render window)
      windowToImageFilter->SetInputBufferTypeToRGBA(); //also record the alpha (transparency) channel
      windowToImageFilter->ReadFrontBufferOff(); // read from the back buffer
      windowToImageFilter->Update();

      vtkSmartPointer<vtkPNGWriter> writer =
        vtkSmartPointer<vtkPNGWriter>::New();
      writer->SetFileName("screenshot2.png");
      writer->SetInputConnection(windowToImageFilter->GetOutputPort());
      writer->Write();

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(Screenshot)

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

    add_executable(Screenshot MACOSX_BUNDLE Screenshot.cxx )

    target_link_libraries(Screenshot ${VTK_LIBRARIES})

### Download and Build Screenshot

Danger

The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.

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

    cd Screenshot/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:

    ./Screenshot

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.