3.1 Converting fax files

I recommend getting the ‘pbmplus’ package written by Jeff Poskanzer, which includes lots of small programs to convert various bitmap formats into a portable intermediate format (pbm) that can easily be converted to fax format with the pbm2g3 program. Further, it comes with lots of tools to scale, flip, and otherwise manipulate the pbm bitmaps. Be warned: it includes its own version of G3 conversion programs (pbmtog3 and g3topbm), so be careful which one you use. The programs in the mgetty package (pbm2g3 and g32pbm) behave slightly different (that is, they work!), and are significantly faster. Note that the pbmplus package does not include a graphical front end.

The pbmplus package can be found on most major FTP sites, e.g. on ftp.x.org in the /contrib directory. See ftp.

If you want to view the images using X11, you should get one of the many image viewers, like ‘xview’, ‘xloadimage’ or ‘xv’. See Fax-Tools. A simple, but very fast fax viewer can be found in mgetty/frontends/X11/.

Here are some examples for viewing fax files using g32pbm:

• You can print a fax on a PostScript printer (try ‘lpr -Pps’ if you don’t have ‘lp’):

  cat $faxfile | g32pbm | pnmtops -noturn | lp -dest postscript
  

• or on an Epson-LQ, scaled for fine resolution (use -yscale 1.84 for normal resolution):

  cat $file | g32pbm | pnmscale -xscale 1.76 -yscale 0.92 |\
      pgmtopbm | pbmtodot -360x180| lp -o epson -
  

• or you could view it using X11 via one of the following commands:

  $ viewfax -v $file
  
  $ cat $file | g32pbm >/tmp/fax.pbm ; xloadimage /tmp/fax.pbm
  
  $ g32pbm $file | xv -
  

There are three easy ways to create g3 fax files, either use pbm2g3 (included in this package. Do not use pbmtog3 from the pbmplus toolkit. See pbmtog3.), use GhostScript (GNU Software, can be found on prep.ai.mit.edu) which contains a “digifax” driver that will produce the required format, or try Chris Lewis’ ‘hp2pbm’ package which will convert HP Laserjet print files into g3 fax files (hp2hig3 program).

Once you have the right tools, there are lots of ways to create fax files for a wide variety of applications. Here are some examples:

• Ascii files can be converted using ‘pbmtext | pbm2g3’ (use a large font, and don’t convert texts longer than about 50 lines). Alternatively, you can convert ascii files to PostScript using ‘psify’, the ‘pslp.ps’ program from the ghostscript distribution, or similar tools, and feed their output into GhostScript.
• PostScript input can be converted by GhostScript (version 2.4 or higher), using the digifax (‘dfaxhigh’ and ‘dfaxlow’) drivers. It will generate a plain g3 file with a 64 byte additional header, which will be skipped automatically. (You have to generate separate g3 files, one per page).

  A typical call to ghostscript would look like this:

  gs -sDEVICE=dfaxhigh -sOutputFile=/tmp/fax.g3.%d yourdocument.ps
  

  Do not use the “tiffg3” or similar drivers, they will create output files with headers that sendfax does not understand, thus causing the receiving fax machine to reject the data (it will assume that the transmitted headers are garbled data).

  If you use Ghostscript version 3.01 and up, you can use the ‘faxg3’ driver as well, its output is identical to the output of the ‘dfaxhigh’ driver except for the 64 byte header. Besides this, there should not be any difference.

  I have observed that with Ghostscript 5.01, the output of the ‘faxg3’ driver is rendered better than that of the ‘dfaxhigh’ driver. In addition, the former is compiled-in by default, while the latter is not. Thus, the default driver used by faxspool is now (starting with 1.1.7) the ‘faxg3’ driver.

• Bitmaps can be converted using the ‘pbmplus’ tools, but you’ll have to do the proper scaling by hand. Use a pipeline with pbm2g3 at the end.
• TeX dvi files can be converted to PostScript using ‘dvialw’ or ‘dvips’. If you want to get the best possible output quality, you can use Metafont to create a set of 204x196 dpi fonts, which will look a lot better than scaled 300 dpi fonts (look into contrib/dvi-fax for instructions how to do this). You can use the epsf macros to include encapsulated PostScript files, e.g. a scanned signature.
• Another way for TeX file conversion is Ralf Schleicher’s faxdvi package, found at ftp://ftp.leo.org/pub/comp/os/unix/networking/mgetty/faxdvi-1.1.tar.gz. Don’t ask me about, ask him!
• HP-Laserjet files can be translated with Chris Lewis’ hp2pbm package. It contains a program hp2hig3 that will read HP-Laserjet PCL4 files and produce G3 output.

  Warning: the G3 files that hp2hig3 emits lack the leading EOL code, thus causing sendfax to complain and possibly fail. As a quick fix, you can pipe those files through g3cat, it will fix the data.

A rather crude sample conversion program (faxcvt) is provided in the fax directory.

Better conversion, including guessing of the format of the input files, is done by the faxspool program, also provided in the fax directory. See Queuing.