public void DrawText(String text, String path)
        {
            BitmapImage bi = new BitmapImage();
            bi.BeginInit();
            bi.UriSource = new Uri(@"E:\Hulk.gif", UriKind.RelativeOrAbsolute);
            bi.EndInit();

            string sText = "This is a text";
            int nTextHeight = 60;
            DrawingVisual drawingVisual = new DrawingVisual();
            using (DrawingContext drawingContext = drawingVisual.RenderOpen())
            {
                drawingContext.DrawImage(bi, new Rect(0, 0, bi.Width, bi.Height));

                Rect rect = new Rect(0, bi.Height, bi.Width, nTextHeight);
                drawingContext.DrawRectangle(System.Windows.Media.Brushes.LightGray, new Pen(Brushes.Red, 2), rect);

                var formattedText = new System.Windows.Media.FormattedText(sText, System.Globalization.CultureInfo.InvariantCulture,
                    FlowDirection.LeftToRight,
                    new Typeface("Arial"), 12, System.Windows.Media.Brushes.Red);
                formattedText.TextAlignment = TextAlignment.Center;
                double nX = bi.Width / 2;
                double nY = bi.Height + nTextHeight / 2;
                System.Windows.Point pt = new System.Windows.Point(nX, nY - formattedText.Height / 2);
                drawingContext.DrawText(formattedText, pt);
            }
            RenderTargetBitmap bmp = new RenderTargetBitmap((int)bi.Width, (int)bi.Height + nTextHeight, 96, 96, PixelFormats.Pbgra32);
            bmp.Render(drawingVisual);

            GifBitmapEncoder gif = new GifBitmapEncoder();
            gif.Frames.Add(BitmapFrame.Create(bmp));
            using (System.IO.Stream stm = System.IO.File.Create(@"E:\Hulk_2.gif"))
            {
                gif.Save(stm);
            }
        }