本示例可將rtf內部文字和標準圖像轉換為自己可以設定的字體效果和大小的圖像。

 /// <summary>
        /// Rtf 轉 圖像
        /// </summary>
        /// <param name="Rtf_Message">Rtf 內容</param>
        /// <param name="_width">圖像寬度</param>
        /// <param name="ch_Width">每個中文文字的寬度</param>
        /// <param name="en_Width">每個英文文字的寬度</param>
        /// <param name="img_Width">包含的固定樣式圖像的大小-寬度高度相同</param>
        /// <param name="TextColor">文字的顏色</param>
        /// <returns></returns>
        private Bitmap RtfToBitmap (string Rtf_Message, int _width, int ch_Width, int en_Width, int img_Width, Color TextColor)
        {
            RichTextEx Rich_tmp = new RichTextEx() // 臨時Richbox 取得全部內容，重新設置字體
            {
                WordWrap = true,
                ScrollBars = RichTextBoxScrollBars.None,
                BorderStyle = BorderStyle.None,
                Height = 10
            };
            Rich_tmp.Rtf = Rtf_Message;
            Rich_tmp.SelectAll();
            Rich_tmp.SelectionColor = Color.FromArgb(255, 255, 255);
            Rich_tmp.SelectionFont = font;

            int havePic = Regex.Matches(Rich_tmp.Rtf, "Paint.Picture").Count; // 取得包含圖像的數量
            MatchCollection haveTxt = Regex.Matches(Rich_tmp.Text, @"[\u4e00-\u9fa5]", RegexOptions.IgnoreCase | RegexOptions.Singleline); // 取得包含中文的數量
            int haveEn = Rich_tmp.Text.Length - haveTxt.Count; // 取得英文、數字、符號的數量
            if ((haveTxt.Count * ch_Width   havePic * img_Width   haveEn * en_Width) > _width) // 超過限定寬度，為設定的寬度
            {
                Rich_tmp.Width = _width;
            }
            else // 沒超過限定，為實際寬度
            {
                Rich_tmp.Width = haveTxt.Count * ch_Width   havePic * img_Width   haveEn * en_Width; 
            }
            CSetLineSpace.SetLineSpace(Rich_tmp, 390); // 設定行間距
            Rich_tmp.updata(); // 刷新

            if (Rich_tmp.Lines.Length > 1) //如果有多行，獲取行字數最多數的行，設置為圖像寬度
            {
                RichTextEx Rich_branch = new RichTextEx()
                {
                    WordWrap = true,
                    ReadOnly = true,
                    BorderStyle = BorderStyle.None,
                    ScrollBars = RichTextBoxScrollBars.None,
                    Text = Rich_tmp.Text
                };
                for (int t = 0; t < Rich_tmp.ImageList.Count; t  ) // 將Rtf內的圖像，替換為特殊符號“?”，避免重復
                {
                    Rich_branch.Text = Rich_branch.Text.Remove(Rich_tmp.ImageList[t].Img_Location, 1);
                    Rich_branch.Text = Rich_branch.Text.Insert(Rich_tmp.ImageList[t].Img_Location, "?");
                }
                MatchCollection haveZh, haveImg;
                int maxlen = 0, exchange;
                for (int i = 0; i < Rich_branch.Lines.Length; i  )
                {
                    haveZh = Regex.Matches(Rich_branch.Lines[i], @"[\u4e00-\u9fa5]", RegexOptions.IgnoreCase | RegexOptions.Singleline); // // Rtf內部中文數量
                    haveImg = Regex.Matches(Rich_branch.Lines[i], @"?", RegexOptions.IgnoreCase | RegexOptions.Singleline); // Rtf內部圖像的數量
                    exchange = (Rich_branch.Lines[i].Length - haveZh.Count - haveImg.Count) * en_Width   haveZh.Count * ch_Width   haveImg.Count * img_Width; // // Rtf內部英文、符號數量
                    if (exchange > _width)
                    {
                        maxlen = _width;
                        break;
                    }
                    if (maxlen < exchange) maxlen = exchange;
                }
                Rich_tmp.Width = maxlen;
                Rich_branch.Dispose();
            }