.net 生成原图和多张缩略图

        /// <summary>
        /// 按日期生成文件夹名
        /// </summary>
        /// <returns>返回文件夹名</returns>
        private static String DateDir()
        {
            return DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString().PadLeft(2, '0') +
                DateTime.Now.Day.ToString().PadLeft(2, '0');
        }

        /// <summary>
        /// 按GUID生成图片名
        /// </summary>
        /// <returns>返回文件名</returns>
        private static String AutoFileName()
        {
            return KeyUtils.GetNewId().Replace("-", "");
        }

        /// <summary>
        /// 相对文件夹路径
        /// </summary>
        private static String sReturnPath = ConfigurationManager.AppSettings["PicPath"].ToString() + "/" + DateDir();

        /// <summary>
        /// 保存原图
        /// </summary>
        /// <param name="bAfs">图片Byte字节数</param>
        /// <param name="sExtend">图片后缀名</param>
        /// <param name="sPath">原图绝对路径</param>
        /// <returns>返回原图绝对路径</returns>
        public static String SaveOriginalImage(Byte[] bAfs, String sExtend, String sPath)
        {
            sPath = sPath + DateDir();

            try
            {
                if (!Directory.Exists(sPath))
                    Directory.CreateDirectory(sPath);
                //定义并实例化一个内存流，以存放提交上来的字节数组。
                MemoryStream m = new MemoryStream(bAfs);
                //原图绝对路径
                string sPathPicName = sPath + "\" + AutoFileName() + sExtend;
                //原始图片写入到文件夹中
                FileStream f = new FileStream(sPathPicName, FileMode.Create);
                ///把内内存里的数据写入物理文件
                m.WriteTo(f);
                m.Close();
                f.Close();
                f = null;
                m = null;

                return sPathPicName;
            }
            catch (Exception)
            {
                return "";
            }
        }

        /// <summary>
        /// 生成缩略图
　　　　 ///　宽高为0则返回处理后的原图，宽高不为0则返回相应的缩略图
        /// </summary>
        /// <param name="_Model">图片处理模型</param>
        /// <param name="sPathPic">输出缩略图相对路径</param>
        /// <returns>返回缩略图相对路径</returns>
        public static String ReturnThumbnailsImage(ImageModel _Model)
        {
            if (String.IsNullOrEmpty(_Model.OriginalImageUrl))
            {
                return "";
            }
            if (!File.Exists(_Model.OriginalImageUrl))
            {
                return "";
            }

            try
            {
                String sFileName = AutoFileName();
                String sLastPath = _Model.Path + DateDir() + "\" + sFileName + _Model.Extend;

                //从文件取得图片对象   
                System.Drawing.Image image = System.Drawing.Image.FromFile(_Model.OriginalImageUrl);

                _Model.Width = _Model.Width == 0 ? image.Width : _Model.Width;
                _Model.Height = _Model.Height == 0 ? image.Height : _Model.Height;
                //取得图片大小
                Size size = new Size(_Model.Width, _Model.Height);
                //新建一个bmp图片   
                Image bitmap = new Bitmap(size.Width, size.Height);
                //新建一个画板   
                Graphics g = Graphics.FromImage(bitmap);
                //设置高质量插值法   
                g.InterpolationMode = InterpolationMode.High;
                //设置高质量,低速度呈现平滑程度   
                g.SmoothingMode = SmoothingMode.HighQuality;
                //清空一下画布   
                g.Clear(Color.Transparent);
                //在指定位置画图   
                g.DrawImage(image, new Rectangle(0, 0, bitmap.Width, bitmap.Height),
                 GetImageBeginXAndY(_Model.Width,_Model.Height,image.Width,image.Height),
                  GraphicsUnit.Pixel);

                //保存高清晰度的缩略图   
                bitmap.Save(sLastPath, System.Drawing.Imaging.ImageFormat.Jpeg);
                g.Dispose();

                return sReturnPath + "/" + sFileName + _Model.Extend;
            }
            catch (Exception)
            {
                return "";
            }
        }

        /// <summary>
        /// 功能：根据位置计算出绘图的开始点
        /// </summary>
        /// <param name="Towidth">需要生成图片的宽度</param>
        /// <param name="ToHeight">需要生成图片的高度</param>
        /// <param name="Owidth">原图宽度</param>
        /// <param name="OHeight">原图高度</param>
        /// <param name="x">绘图的开始x 点坐标</param>
        /// <param name="y">绘图的开始 y 点坐标</param>
        private static Rectangle GetImageBeginXAndY(int Towidth, int ToHeight, int Owidth, int OHeight)
        {
            int towidth = Towidth;
            int toheight = ToHeight;
            int x = 0;
            int y = 0;
            int ow = Owidth;
            int oh = OHeight;

            if ((double)Owidth / (double)OHeight > (double)Towidth / (double)ToHeight)
            {
                oh = OHeight;
                ow = OHeight * towidth / toheight;
                y = 0;
                x = (Owidth - ow) / 2;
            }
            else
            {
                ow = Owidth;
                oh = Owidth * ToHeight / towidth;
                x = 0;
                y = (OHeight - oh) / 2;
            }
            return new Rectangle(x, y, ow, oh);

        }

        /// <summary>
        /// 生成多张缩略图
        /// </summary>
        /// <param name="sPath">原图绝对路径</param>
        /// <param name="sOriginalImageUrl">原图绝对路径</param>
        /// <param name="sExtend">图片后缀名</param>
        /// <param name="lst_PicPath">图片宽高规则列表</param>
        /// <returns>返回多个缩略图列表</returns>
        public static List<PicThumbnailRuleModel> GetMultiThumbnails(String sPath, String sOriginalImageUrl, String sExtend, List<PicThumbnailRuleModel> lst_PicPath)
        {
            List<PicThumbnailRuleModel> lst_Model = new List<PicThumbnailRuleModel>();

            ImageModel _ImageModel = new ImageModel();
            //绝对文件夹路径
            _ImageModel.Path = sPath;
            _ImageModel.OriginalImageUrl = sOriginalImageUrl;
            _ImageModel.Extend = sExtend;

            for (int i = 0; i < lst_PicPath.Count; i++)
            {
                _ImageModel.Width = lst_PicPath[i].Width;
                _ImageModel.Height = lst_PicPath[i].Height;

                PicThumbnailRuleModel Model = new PicThumbnailRuleModel();
                Model.Width = _ImageModel.Width;
                Model.Height = _ImageModel.Height;
                Model.PicThumbnailsInfo = UploadImageComm.ReturnThumbnailsImage(_ImageModel);
                lst_Model.Add(Model);
            }
            return lst_Model;
        }

　　　　　

    /// <summary>
    /// 图片缩略图规则模型
    /// </summary>
    public class PicThumbnailRuleModel
    {
        /// <summary>
        /// 设置生成图片宽度
        /// </summary>
        public Int32 Width { get; set; }

        /// <summary>
        /// 设置生成图片高度
        /// </summary>
        public Int32 Height { get; set; }

        /// <summary>
        /// 生成之后的图片名称
        /// </summary>
        public String PicThumbnailsInfo { get; set; }
    }