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G3topbm User Manual(0)							   G3topbm User Manual(0)

NAME
       g3topbm - convert a Group 3 fax file into a PBM image

SYNOPSIS
       g3topbm	[-kludge] [-reversebits] [-stretch] [-width=pixels | paper_size={A3|A4|A5|A6|B4}]
       [-stop_error] [g3file]

       Minimum unique abbreviation of option is acceptable.  You may use double  hyphens  instead
       of  single  hyphen to denote options.  You may use white space in place of the equals sign
       to separate an option name from its value.

DESCRIPTION
       This program is part of Netpbm(1)

       g3topbm reads a Group 3 fax file with MH (Modified Huffman) compression as input and  pro-
       duces a PBM image as output.

       g3topbm tolerates various deviations from the standard, so as to recover some of the image
       if there was a transmission error.  One thing it tolerates is  lines  of  varying  length.
       The  standard requires all the lines to be the same length; g3topbm makes the output image
       as wide as the longest line in the input and pads the others on the right.  It  warns  you
       when it does this.

       You can use the stop_error option to make g3topbm insist on valid input.

       There is no Netpbm program that understands the other G3 fax compression methods: MR (Mod-
       ified Read) and MMR (Modified Modified Read).

       Note that the Group 3 fax file format does not include any kind of  a  signature  so  that
       g3topbm	might verify it's actually looking at a G3 file or that the compression method is
       MH.  The program will interpret any sequence of bytes you give it as  if  it  is  G3  and,
       while typically issuing a lot of error messages about the file not conforming to the G3 MH
       format, will produce output (unless you use  -stoperror).   In  particular,  if	you  feed
       g3topbm an MR or MMR file, it will not tell you of your mistake.

       There are subformats of TIFF that use the Group 3 fax encodings inside.	See tifftopnm.

OPTIONS
       -kludge
	      Tells  g3topbm  to ignore the first few lines of the file; sometimes fax files have
	      some junk at the beginning.

       -reversebits
	      Tells g3topbm to interpret bits least-significant first,	instead  of  the  default
	      most-significant	first.	Apparently some fax modems do it one way and others do it
	      the other way.  If you get a whole bunch of 'bad code  word'  messages,  try  using
	      this option.

       -stretch
	      This  option tells g3topbm to stretch the image vertically by duplicating each row.
	      This is for the low-quality transmission mode.

       -width=pixels
	      This option tells g3topbm that the image is supposed to be pixels pixels wide.   If
	      any  line  in  it is not that size, g3topbm issues a warning or fails, depending on
	      whether you specify -stop_error.

	      You cannot specify both -width and -paper_size.

	      This option was new in Netpbm 10.33 (March 2006).

       -paper_size={A3,A4,A5,A6,B4}
	      This option tells g3topbm for what size paper this image is supposed to be  format-
	      ted.   g3topbm  uses the width of the paper the same way as with the -width option.
	      g3topbm does not use the height of the paper for anything.

	      You cannot specify both -width and -paper_size.

	      This option was new in Netpbm 10.33 (March 2006).

       -stop_error
	      This option tells g3topbm to fail when it finds a problem  in  the  input.   'Fail'
	      means it terminates with a nonzero status code with the contents of the output file
	      undefined.

	      If you don't specify this option, g3topbm does its best to work around input errors
	      and  salvage  as much of the image as possible in the output image.  It first tries
	      to resynchronize to a later line by searching for the  next  End	Of  Line  marker,
	      skipping any lines or partial lines in between.  It saves the beginning of the line
	      in which it encountered the problem.  If the input file ends  prematurely,  g3topbm
	      produces output containing the lines up to where it encountered the problem.

	      g3topbm issues warning messages when it continues in spite of input errors.

	      This  option  was  new  in Netpbm 10.24 (August 2004).  Before that, g3topbm always
	      failed when it encountered premature EOF and never failed when it encountered other
	      problems.

SEE ALSO
       pbmtog3(1) , tifftopnm(1) , pbm(1)

       faxformats(1)

netpbm documentation			 03 December 2008		   G3topbm User Manual(0)
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