分享一個RTF轉Image的方法，求高手最佳化

        /// <summary>
        /// rtf轉image
        /// </summary>
        /// <returns></returns>
        public Image GetImageFromRtf()
        {
            if (this.SelectionType != RichTextBoxSelectionTypes.Object) return null;
            Graphics graphics = null;
            MemoryStream stream = null;
            Metafile metafile = null;
            try
            {
                var props = this.SelectedRtf.Split(new char[] { '\\' }, StringSplitOptions.RemoveEmptyEntries);

                int pich = int.Parse((from x in props where x.Contains("pich") select x).First<string>().Remove(0, 4));
                int picw = int.Parse((from x in props where x.Contains("picw") select x).First<string>().Remove(0, 4));
                // Get the horizontal and vertical resolutions at which the object is
                using (graphics = this.CreateGraphics())
                {
                    xDpi = graphics.DpiX;
                    yDpi = graphics.DpiY;
                }
                // Calculate the current width of the image in (0.01)mm
                int imageWidth = (int)Math.Round(picw * xDpi / HMM_PER_INCH);

                // Calculate the current height of the image in (0.01)mm
                int imageHeight = (int)Math.Round(pich * yDpi / HMM_PER_INCH);
                var lines = this.SelectedRtf.Split(Environment.NewLine.ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
                List<byte> imageBytes = new List<byte>();
                for (int i = 2; i < lines.Length - 1; i++)
                {
                    for (int j = 0; j < lines[i].Length; j+=2)
                    {
                        imageBytes.Add(Byte.Parse(new string(new char[] { lines[i][j], lines[i][j + 1] }),
                            System.Globalization.NumberStyles.HexNumber));
                    }
                }
                stream = new MemoryStream(imageBytes.ToArray());
                metafile = new Metafile(stream);
                Image img = metafile.GetThumbnailImage(imageWidth, imageHeight, null, IntPtr.Zero);
                return img;
            }
            finally
            {
                if (graphics != null)
                    graphics.Dispose();
                if (metafile != null)
                    metafile.Dispose();
                if (stream != null)
                    stream.Close();
            }
        }