private void button3_Click(object sender, EventArgs e)

        {

            using (OpenFileDialog ofd = new OpenFileDialog())

            {

                ofd.Filter = "图片|*.jpg;*.png;*.gif;*.jpeg;*.bmp";

                if (ofd.ShowDialog() == DialogResult.OK)

                {

                    using (FileStream file = new FileStream(ofd.FileName, FileMode.Open))

                    {

                        var img = CompressionImage(file, 50L);

                        MessageBox.Show(CreateImageFromBytes(AppDomain.CurrentDomain.BaseDirectory + @"\" + Guid.NewGuid().ToString(), img));

                    }

                }

            }

        }

        ///

        public static Image BytesToImage(byte[] buffer)

        {

            MemoryStream ms = new MemoryStream(buffer);

            Image image = System.Drawing.Image.FromStream(ms);

            return image;

        }

        ///

        public static string CreateImageFromBytes(string fileName, byte[] buffer)

        {

            string file = fileName;

            Image image = BytesToImage(buffer);

            ImageFormat format = image.RawFormat;

            if (format.Equals(ImageFormat.Jpeg))

            {

                file += ".jpeg";

            }

            else if (format.Equals(ImageFormat.Png))

            {

                file += ".png";

            }

            else if (format.Equals(ImageFormat.Bmp))

            {

                file += ".bmp";

            }

            else if (format.Equals(ImageFormat.Gif))

            {

                file += ".gif";

            }

            else if (format.Equals(ImageFormat.Icon))

            {

                file += ".icon";

            }

            System.IO.FileInfo info = new System.IO.FileInfo(file);

            System.IO.Directory.CreateDirectory(info.Directory.FullName);

            File.WriteAllBytes(file, buffer);

            return file;

        }

        /// ///

        /// 圖片流

        /// 壓縮質量0-100之間 數值越大質量越高

        ///

        private byte[] CompressionImage(Stream fileStream, long quality)

        {

            using (System.Drawing.Image img = System.Drawing.Image.FromStream(fileStream))

            {

                using (Bitmap bitmap = new Bitmap(img))

                {

                    ImageCodecInfo CodecInfo =  GetEncoder(img.RawFormat);

                    System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;

                    EncoderParameters myEncoderParameters = new EncoderParameters(1);

                    EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, quality);

                    myEncoderParameters.Param[0] = myEncoderParameter;

                    using (MemoryStream ms = new MemoryStream())

                    {

                        bitmap.Save(ms, CodecInfo, myEncoderParameters);

                        myEncoderParameters.Dispose();

                        myEncoderParameter.Dispose();

                        return ms.ToArray();

                    }

                }

            }

        }

        private static ImageCodecInfo GetEncoder(ImageFormat format)

        {

            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();

            foreach (ImageCodecInfo codec in codecs)

            {

                if (codec.FormatID == format.Guid)

                { return codec; }

            }

            return null;

        }