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# Screenshot

VTKEx/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.

Other languages

See (Python), (Java)

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### 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 <vtkVersion.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);
    #if VTK_MAJOR_VERSION >= 8 || VTK_MAJOR_VERSION == 8 && VTK_MINOR_VERSION >= 90
      windowToImageFilter->SetScale(2); // image quality
    #else
      windowToImageFilter->SetMagnification(2); //image quality
    #endif
      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 3.3 FATAL_ERROR)

    project(Screenshot)

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

### Download and Build Screenshot

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

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