C# 图像叠加（gdkpixbufoverlay）

如何将GStreamer应用程序中的图像覆盖添加到管道？提前谢谢

var image = ElementFactory.Make("gdkpixbufoverlay");
image["location"] = @"D:\camera.png";
image["overlay-height"] = 200;
image["overlay-width"] = 200;
image["offset-x"] = 100;
image["offset-y"] = 100;

pipeline.Add(image);

少了什么

var img = ElementFactory.Make("gdkpixbufoverlay");
        img["location"] = @"D:\camera.png";
        img["overlay-height"] = 200;
        img["overlay-width"] = 200;
        img["offset-x"] = 0.1;
        img["offset-y"] = 0.1;            
        pipeline.Add(img);
        var ret = pad.Link(img.GetStaticPad("sink"));
        if (ret != PadLinkReturn.Ok)
        {
            sysDbg.WriteLine("Error linking image overlay.");
        }
        img.SyncStateWithParent();
        pad = img.GetStaticPad("src");