void grabImage(OSG::Image *img)
{
    OSG::UInt8* data = img->editData();

    // for this example, just fill it with random junk
    if(changeOnlyPart)
    {
        // Just change a small rectangular area
        OSG::UInt32 x = rand() % (img->getWidth() - 100);
        OSG::UInt32 y = rand() % (img->getHeight() - 100);
        OSG::UInt32 w = rand() % 100;
        OSG::UInt32 h = rand() % 100;
        OSG::UInt32 bpp = img->getBpp();
        OSG::UInt32 bpl = img->getWidth() * bpp;
        OSG::UInt32 bytes = w * bpp;

        data += y * bpl + x * bpp;

        OSG::UInt8 val = ((rand() & 0x7f) + 0x80);

        for(OSG::UInt32 i = h; i > 0; --i, data += bpl)
        {
            OSG::UInt8 *d = data;

            for(OSG::UInt32 j = bytes; j > 0; --j)
                *d++ = val;
        }

        // If only a part of the image changed, only that part needs to
        // be updated. The speed of the update operation is pretty
        // directly dependent on the amount of data changed.
        texObj->imageContentChanged(x, x + w, y, y + h);
    }
    else
    {

        // Fill the whole picture

        for(OSG::UInt32 i = img->getHeight(); i > 0; --i)
        {
            OSG::UInt8 val = ((rand() & 0x3f) + 0x80);

            for(OSG::UInt32 j = img->getWidth() * img->getBpp(); j > 0; --j)
                *data++ = val;
        }

        // Everything changed
        texObj->imageContentChanged();
    }
}

// Initialize GLUT & OpenSG and set up the scene
int main(int argc, char **argv)
{
    // OSG init
    OSG::osgInit(argc,argv);

    // GLUT init
    int winid = setupGLUT(&argc, argv);

    {
        // the connection between GLUT and OpenSG
        OSG::GLUTWindowRefPtr gwin = OSG::GLUTWindow::create();

        gwin->setGlutId(winid);
        gwin->init();

        // create the scene
        OSG::NodeRefPtr torus = OSG::makeTorus( .5, 2, 16, 32 );
        OSG::NodeRefPtr scene = OSG::Node::create();

        trans = OSG::Transform::create();

        scene->setCore(trans);
        scene->addChild(torus);

        // Create the parts needed for the video background
        OSG::UInt32 width  = 640;
        OSG::UInt32 height = 480;

        // get the desired size from the command line
        if(argc >= 3)
        {
            width  = atoi(argv[1]);
            height = atoi(argv[2]);
        }

        // To check OpenGL extensions, the Window needs to have run through
        // frameInit at least once. This automatically happens when rendering,
        // but we can't wait for that here.

        gwin->activate ();
        gwin->frameInit();

        // Now we can check for OpenGL extensions
        hasNPOT = gwin->hasExtension("GL_ARB_texture_non_power_of_two");

        // Print what we've got
        SLOG << "Got " << (isPOT?"":"non-") << "power-of-two images and "
            << (hasNPOT?"can":"cannot") << " use NPOT textures, changing "
            << (changeOnlyPart?"part":"all")
            << " of the screen"
            << std::endl;

        // Ok, now for the meat of the code...
        // first we need an Image to hold the picture(s) to show
        image = OSG::Image::create();

        // set the image's size and type, and allocate memory
        // this example uses RGB. On some systems (e.g. Windows) BGR
        // or BGRA might be faster, it depends on how the images are
        // acquired

        image->set(OSG::Image::OSG_RGB_PF, width, height);



        // Now create the texture to be used for the background
        texObj = OSG::TextureObjChunk::create();

        // Associate image and texture
        texObj->setImage(image);

        // Set filtering modes. LINEAR is cheap and good if the image size
        // changes very little (i.e. the window is about the same size as
        // the images).

        texObj->setMinFilter(GL_LINEAR);
        texObj->setMagFilter(GL_LINEAR);

        // Set the wrapping modes. We don't need repetition, it might actually
        // introduce artifactes at the borders, so switch it off.

        texObj->setWrapS(GL_CLAMP_TO_EDGE);
        texObj->setWrapT(GL_CLAMP_TO_EDGE);

        // Newer versions of OpenGL can handle NPOT textures directly.
        // OpenSG will do that internally automatically.
        //
        // Older versions need POT textures. By default OpenSG
        // will scale an NPOT texture to POT while defining it.
        // For changing textures that's too slow.
        // So tell OpenSG not to scale the image and adjust the texture
        // coordinates used by the TextureBackground (see below).

        texObj->setScale(false);

        // Create the background

        OSG::TextureBackgroundRefPtr back = OSG::TextureBackground::create();

//.........这里部分代码省略.........