C#图片压缩上传

   /// <summary>
        /// 压缩图片
        /// </summary>
        /// <param name="iSource">图片文件</param>
        /// <param name="outPath">路径</param> 例如 var outPath = Path.Combine(Request.MapPath("~/Upload"), Path.GetFileName(file.FileName));
        /// <param name="flag">值越大代表图片质量越好，一般默认控制在50为最佳压缩质量</param>
        /// <returns></returns>
        public static bool ReduceImage(Image iSource, string outPath, int flag)
        {
            ImageFormat tFormat = iSource.RawFormat;
            EncoderParameters ep = new EncoderParameters();
            long[] qy = new long[1];
            qy[0] = flag;
            EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
            ep.Param[0] = eParam;
            try
            {
                ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageDecoders();
                ImageCodecInfo jpegICIinfo = null;
                for (int x = 0; x < arrayICI.Length; x++)
                {
                    if (arrayICI[x].FormatDescription.Equals("JPEG"))
                    {
                        jpegICIinfo = arrayICI[x];
                        break;
                    }
                }
                if (jpegICIinfo != null)
                    iSource.Save(outPath, jpegICIinfo, ep);
                else
                    iSource.Save(outPath, tFormat);
                return true;
            }
            catch
            {
                return false;
            }
            finally
            {
                iSource.Dispose();
            }
        }

　　图片类型转换

 /// <summary>
        ///byte[] 图片转换
        /// </summary>
        /// <param name="buffer"></param>
        /// <returns></returns>
        public static Image BytesToImage(byte[] buffer)
        {
            MemoryStream ms = new MemoryStream(buffer);
            Image image = System.Drawing.Image.FromStream(ms);
            return image;
        }

  /// <summary>
        /// 使用流方式,上传并保存文件
        /// </summary>
        /// <param name="s">文件流</param>
        /// <param name="savepath">保存文件路径</param>
        /// <param name="warning">处理警告信息,若为空,则处理成功</param>
        /// <returns>返回文件保存完整路径</returns>
        public static string uploadbystream(Stream s, string savepathFolder, out string warning)
        {
            try
            {
                int be = 0;
                if (s.Length > 0)
                {
                    MemoryStream ms = new MemoryStream();

                    while ((be = s.ReadByte()) != -1)
                    {
                        ms.WriteByte((byte)be);
                    }
                    string reletiveFolder = "UploadFile\\ManageImage\\" + savepathFolder + "\\" + DateTime.Now.Year + "\\" + DateTime.Now.Month;
                    string folderPath = HttpContext.Current.Server.MapPath("~/") + reletiveFolder;
                    if (!Directory.Exists(folderPath))
                        Directory.CreateDirectory(folderPath);
                    string filename = DateTime.Now.ToString("yyyyMMddHHmmss") + ".jpg";
                    string newpath = folderPath + "\\" + filename;

                    string lastpath = "";
                    lastpath = newpath;
                    //FileExistMapPath(newpath, FileCheckModel.M, out lastpath);

                    FileStream fs = new FileStream(lastpath, FileMode.Create);

                    ms.WriteTo(fs);

                    //释放
                    ms.Dispose();
                    fs.Dispose();

                    warning = "";
                    return reletiveFolder + "\\" + filename;
                }

                warning = "error";
                return "";
            }
            catch (Exception ex)
            {
                warning = "error" + ex.Message;
                return "";
            }
        }