C#生成缩略图

/// <summary>
        /// 获取等比例缩放图片的方法
        /// </summary>
        /// <param name="imgPath">待缩放及保存图片的路径</param>
        /// <param name="format">缩放图片保存的格式</param>
        /// <param name="scaling">要保持的宽度或高度</param>
        /// <param name="keepWidthOrHeight">如果为true则保持宽度为scaling，否则保持高度为scaling</param>
        /// <returns></returns>
        public bool GetThumbnail(string imgPath, System.Drawing.Imaging.ImageFormat format, int scaling, bool keepWidthOrHeight)
        {
            File.Copy(imgPath, imgPath + ".bak");
            try
            {
                using (System.Drawing.Bitmap myBitmap = new System.Drawing.Bitmap(imgPath))
                {
                    int width = 0;
                    int height = 0;
                    int tw = myBitmap.Width;//图像的实际宽度
                    int th = myBitmap.Height;//图像的实际高度
                    if (keepWidthOrHeight)//保持宽度
                    {
                        #region 自动保持宽度
                        if (scaling >= tw)
                        {
                            width = tw;
                            height = th;
                        }
                        else
                        {
                            double ti = Convert.ToDouble(tw) / Convert.ToDouble(scaling);
                            if (ti == 0d)
                            {
                                width = tw;
                                height = th;
                            }
                            else
                            {
                                width = scaling;
                                height = Convert.ToInt32(Convert.ToDouble(th) / ti);
                            }
                        }
                        #endregion
                    }
                    else
                    {
                        #region 自动保持高度
                        if (scaling >= th)
                        {
                            width = tw;
                            height = th;
                        }
                        else
                        {
                            double ti = Convert.ToDouble(th) / Convert.ToDouble(scaling);
                            if (ti == 0d)
                            {
                                width = tw;
                                height = th;
                            }
                            else
                            {
                                width = Convert.ToInt32(Convert.ToDouble(tw) / ti);
                                height = scaling;
                            }
                        }
                        #endregion
                    }
                    using (System.Drawing.Image myThumbnail = myBitmap.GetThumbnailImage(width, height, null, IntPtr.Zero))
                    {
                        myBitmap.Dispose();
                        File.Delete(imgPath);
                        myThumbnail.Save(imgPath);
                    }
                }
                File.Delete(imgPath + ".bak");

                return true;
            }
            catch
            {
                return false;
            }
            
        }