/// <summary>
    /// 壓縮圖片 /// </summary>
    /// <param name="fileStream">圖片流</param>
    /// <param name="quality">壓縮質量0-100之間 數值越大質量越高</param>
    /// <returns></returns>
    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();
                }
            }
        }
    }
調用:CompressionImage(stream,0L)//最低質量 1M jpg圖大概能壓成180k左右