OpenSceneGraph: Creating background image

BackgroundImage.cpp

// create a camera to set up the projection and model view matrices, and the subgraph to draw in the HUD
osg::ref_ptr<osg::Camera> camera = new osg::Camera();

// set the view matrix
camera->setReferenceFrame(osg::Camera::ABSOLUTE_RF);
// use identity view matrix so that children do not get (view) transformed
camera->setViewMatrix(osg::Matrix::identity());
// set the projection matrix to be of width and height of 1
camera->setProjectionMatrix(osg::Matrix::ortho2D(0, 1.0f, 0, 1.0f));
// set resize policy to fixed
camera->setProjectionResizePolicy(osg::Camera::ProjectionResizePolicy::FIXED);

// only clear the depth buffer
camera->setClearMask(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

// draw subgraph before main camera view.
camera->setRenderOrder(osg::Camera::NESTED_RENDER);

// we don't want the camera to grab event focus from the viewers main camera(s).
camera->setAllowEventFocus(false);

osg::StateSet* cameraStateSet = camera->getOrCreateStateSet();
cameraStateSet->setRenderBinDetails(1, "RenderBin");
cameraStateSet->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF);

// add to this camera a subgraph to render
{

    osg::ref_ptr<osg::Geode> geode{ new osg::Geode() };

    auto stateset = geode->getOrCreateStateSet();
    stateset->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
    {
        auto backgroundImage = osgDB::readImageFile("data/images/bg_ragnarok_01.bmp");
        auto texturedQuad = osg::createTexturedQuadGeometry(
            osg::Vec3(0.f, 0.f, 0.f),
            osg::Vec3(1.0f, 0.f, 0.f),
            osg::Vec3(0.f, 1.0f, 0.f),
            0.f,
            0.f,
            backgroundImage->s(),
            backgroundImage->t());
        auto textureRect = new osg::TextureRectangle(backgroundImage); textureRect->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);
        textureRect->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);
        textureRect->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE);
        textureRect->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE);
        texturedQuad->getOrCreateStateSet()->setTextureAttributeAndModes(0, textureRect, osg::StateAttribute::ON);
        texturedQuad->getOrCreateStateSet()->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF);
        geode->addDrawable(texturedQuad);
    }

    if (!camera->addChild(geode))
    {
        osg::notify(osg::NotifySeverity::WARN) << "Failed to add geode" << std::endl;
    }
}
osgViewer::Viewer::Windows windows;
viewer.getWindows(windows);

if (windows.empty())
{
    return;
}

// set up cameras to render on the first window available.
auto window = windows[0];
camera->setGraphicsContext(window);
auto windowTraits = window->getTraits();
camera->setViewport(0, 0, windowTraits->width, windowTraits->height);

auto group = dynamic_cast<osg::Group*>(viewer.getSceneData());
if (nullptr == group)
{
    osg::notify(osg::NotifySeverity::WARN) << "Failed to add camera" << std::endl;
    return;
}
group->addChild(camera.get());

Second revision of this solved my problem

Hi. I have a Problem With This Code.After Define "windows"(line 57) Without any initializing For That Check "(windows.empty())"(line 60) and The program return And Exit.Where is My Mistake?Please help Me.THX