//add by ladofwind,change bitmap size and resolution
                Bitmap bmpSource = new Bitmap(((Bitmap)this.images[0]), 1653, 2338);
                int iSourceWidth = bmpSource.Width;
                int iSourceHeight = bmpSource.Height;
                float fSourceHorResolution = bmpSource.HorizontalResolution;
                float fSourceVerResolution = bmpSource.VerticalResolution;
                //dpi reset
                float fTargetHorResolution = 200;
                float fTargetVerResolution = 200;
                Bitmap bmpTarget = new Bitmap(1653, 2338);
                Graphics g = Graphics.FromImage(bmpTarget);
                g.DrawImage(bmpSource, 0, 0, iSourceWidth, iSourceHeight);
                bmpTarget.SetResolution(fTargetHorResolution, fTargetVerResolution);

                ImageCodecInfo info = GetEncoderInfo("image/tiff");
                Encoder enc = Encoder.SaveFlag;
                EncoderParameters ep = null;
                if (this.pbMain.Image.PixelFormat == PixelFormat.Format1bppIndexed) //G4 compression
                {
                    ep = new EncoderParameters(3);
                    ep.Param[0] = new EncoderParameter(Encoder.Compression, (long)EncoderValue.CompressionCCITT4);
                    ep.Param[1] = new EncoderParameter(Encoder.Quality, 0L);// 
                    ep.Param[2] = new EncoderParameter(Encoder.ColorDepth, 1L); // black/white
                }


                bmpTarget.Save(filename,info,ep); // exception thrown