private string ImgComPress(string fromBase64)

        {

            Bitmap bitMap = new Bitmap(new MemoryStream(Convert.FromBase64String(fromBase64)));

            //Bitmap bitMap = new Bitmap(Server.MapPath("./1.jpg"));

            ImageCodecInfo jgpEncoder = GetEncoder(ImageFormat.Jpeg);

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

            EncoderParameters myEncoderParameters = new EncoderParameters(1);

            EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, 80L);

            myEncoderParameters.Param[0] = myEncoderParameter;

            Bitmap newbitMap = null;

            if (bitMap.Height > 1080)

            {

                float newWidth = ((float)bitMap.Width / bitMap.Height) * 1080;

                newbitMap = new Bitmap(bitMap, (int)newWidth, 1080);//从指定的现有图像并使用指定的大小初始化 Bitmap 类的新实例。

            }

            using (MemoryStream ms = new MemoryStream())

            {

                if (newbitMap != null)

                {

                    newbitMap.Save(ms, jgpEncoder, myEncoderParameters);

                }

                else

                {

                    bitMap.Save(ms, jgpEncoder, myEncoderParameters);

                    bitMap.Save(Server.MapPath("./2.jpg"));

                    bitMap.Save(Server.MapPath("./2_1.jpg"), jgpEncoder, myEncoderParameters);

                }

                if (ms.Length >= 1)

                {

                    return Convert.ToBase64String(ms.GetBuffer());

                }

            }

            return fromBase64;

        }

        private ImageCodecInfo GetEncoder(ImageFormat format)

        {

            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();

            foreach (ImageCodecInfo codec in codecs)

            {

                if (codec.FormatID == format.Guid)

                {

                    return codec;

                }

            }

            return null;

        }