GDI+ throws "Parameter is not valid" exception when calling Image.Save with Encoder.Transformation

                       using (Image b = Image.FromFile("somefile.jpg"))
                    {

                        using (Graphics g = Graphics.FromImage(b))
                        {
g.DrawString("some text", new Font("Arial", 10), Brushes.Yellow, b.Size.Width, b.Size.Height);
                            String newName = "newfile.jpg";

                            ImageCodecInfo encoderInfo = GetEncoderInfo("image/jpeg");

                            EncoderParameters encParams = new EncoderParameters(1);
                            encParams.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);
                            //encParams.Param[1] = new EncoderParameter(System.Drawing.Imaging.Encoder.Transformation,(long)EncoderValue.TransformRotate90);
                            b.Save(newName, encoderInfo, encParams);
}
}