/// <summary>
        /// 图片压缩方法
        /// </summary>
        /// <param name="sFile">文件流FileUpload.PostedFile.InputStream</param>
        /// <param name="dFile">要保存的位置</param>
        /// <param name="flag">清晰度</param>
        /// <returns></returns>

public bool GetPicThumbnail(Stream sFile, string dFile, int dHeight, int dWidth, int flag)
 {

　　//System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);sfile这个参数就是文件原始路径，用这个方法就会有权限的设置所以最好还是用文件流读取

　　System.Drawing.Image iSource = System.Drawing.Image.FromStream(sFile);

　　ImageFormat tFormat = iSource.RawFormat;

　　int sW = 0, sH = 0;

　　 //按比例缩放
       Size tem_size = new Size(iSource.Width, iSource.Height);

　　 if (tem_size.Width > dHeight || tem_size.Width > dWidth) //将**改成c#中的或者操作符号
            {
                if ((tem_size.Width * dHeight) > (tem_size.Height * dWidth))
                {
                    sW = dWidth;
                    sH = (dWidth * tem_size.Height) / tem_size.Width;
                }
                else
                {
                    sH = dHeight;
                    sW = (tem_size.Width * dHeight) / tem_size.Height;
                }
            }

　　else
            {
                sW = tem_size.Width;
                sH = tem_size.Height;
            }

　　     Bitmap ob = new Bitmap(dWidth, dHeight);
            Graphics g = Graphics.FromImage(ob);
            g.Clear(Color.WhiteSmoke);
            g.CompositingQuality = CompositingQuality.HighQuality;
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);
            g.Dispose();

　　//以下代码为保存图片时，设置压缩质量
            EncoderParameters ep = new EncoderParameters();
            long[] qy = new long[1];
            qy[0] = flag;//设置压缩的比例1-100
            EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
            ep.Param[0] = eParam;
            try
            {
                ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
                ImageCodecInfo jpegICIinfo = null;
                for (int x = 0; x < arrayICI.Length; x++)
                {
                    if (arrayICI[x].FormatDescription.Equals("JPEG"))
                    {
                        jpegICIinfo = arrayICI[x];
                        break;
                    }
                }
                if (jpegICIinfo != null)
                {
                    ob.Save(dFile, jpegICIinfo, ep);//dFile是压缩后的新路径
                }
                else
                {
                    ob.Save(dFile, tFormat);
                }
                return true;
            }
            catch
            {
                return false;
            }
            finally
            {
                iSource.Dispose();
                ob.Dispose();
            }

}