Bitmap Bi=new Bitmap("C:\img.tif");SaveFileDialog sfdlg = new SaveFileDialog();sfdlg.Filter = "bmp文件(*.BMP)|*.BMP|All File(*.*)|*.*";sfdlg.ShowDialog();EncoderParameters eps = new EncoderParameters(1);eps.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Compression, (long)EncoderValue.CompressionCCITT4);myImageCodecInfo = GetEncoderInfo("image/tiff");Bi.Save(sfdlg.FileName, myImageCodecInfo, eps);