using tiffv3.3 with Alden (Group 3) Fax charts


TIFF is the Tag Image File Format. It is file format suitable for archiving 
image data. There is a portable, freely available library and utilities 
available via ftp from sgi.com in /graphics/tiff.

As aspect of TIFF that makes it interesting to this discussion is that there is a defined 
"fax" format in the space of TIFF possibilities.  What this format does is 
simply adds some TIFF tags to the Group 3 (or 4) FAX data, leaving the data essentially 
unchanged. By stripping fax padding or using Group 4 (2d) encoding, the resulting file 
may be actually be slightly smaller.  TIFF aware utilities (of which there are many) can 
then handle the data. The advantage is that the image data goes through a minumum 
transformation pipeline going from g3 to tiff to whatever.

Here are some useful pipe commands using the tiff package.

% fax2tiff -M -o 2020.tif 2020.g3

Converts to tiff from g3. The '-M' option is required (and took me a long time 
to figure out :-).

_From here you can use xv. Printing the tiff file to postscript there are at 
least 2 options:

% tiff2ps 2020.tif | lpr

or

% fax2ps fax2ps.tif | lpr

The latter form is optimized to the FAX tiff file (like you produced) and uses 
a PostScript compression scheme to reduce the amount of data which goes over 
the wire from your host computer to your printer by quite a bit: For a typical 
file 137649 byte (fax tif) input file, from 967921 bytes to 347835 bytes. This 
can be a big win if your printer is on a serial port. If you have an ethernet 
printer, the additional compute overhead (on your host, AND on your printer) 
probably makes this the PostScript compression not such a good idea.

Have Fun.

-glenn