/// <summary>

        /// 根据指定尺寸得到按比例缩放的尺寸,返回true表示以更改尺寸

        /// </summary>

        /// <param name="picWidth">图片宽度</param>

        /// <param name="picHeight">图片高度</param>

        /// <param name="specifiedWidth">指定宽度</param>

        /// /// <param name="specifiedHeight">指定高度</param>

        /// <returns>返回true表示以更改尺寸</returns>

        private bool GetPicZoomSize(ref int picWidth, ref int picHeight, int specifiedWidth, int specifiedHeight)

        {

            int sW = 0, sH = 0;

            Boolean isZoomSize = false;

            //按比例缩放

            Size tem_size = new Size(picWidth, picHeight);

            if (tem_size.Width > specifiedWidth || tem_size.Height > specifiedHeight) //将**改成c#中的或者操作符号

            {

                if ((tem_size.Width * specifiedHeight) > (tem_size.Height * specifiedWidth))

                {

                    sW = specifiedWidth;

                    sH = (specifiedWidth * tem_size.Height) / tem_size.Width;

                }

                else

                {

                    sH = specifiedHeight;

                    sW = (tem_size.Width * specifiedHeight) / tem_size.Height;

                }

                isZoomSize = true;

            }

            else

            {

                sW = tem_size.Width;

                sH = tem_size.Height;

            }

            picHeight = sH;

            picWidth = sW;

            return isZoomSize;

        }

        /// <summary>

        /// 无损压缩图片

        /// </summary>

        /// <param name="sFile">原图片</param>

        /// <param name="dFile">压缩后保存位置</param>

        /// <param name="dHeight">高度</param>

        /// <param name="dWidth">宽度</param>

        /// <param name="flag">压缩质量 1-100</param>

        /// <returns></returns>

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

        {

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

            ImageFormat tFormat = iSource.RawFormat;

            int sW = iSource.Width, sH = iSource.Height;

            GetPicZoomSize(ref sW, ref sH, dWidth, dHeight);

            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();

            }

        }