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

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

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

       Minimum unique abbreviation of option is	acceptable.  You may use  dou-
       ble  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.

       This program is part of Netpbm(1).

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

       g3topbm tolerates various deviations from the standard, so  as  to  re-
       cover  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 in-

       There is	no Netpbm program that understands the other G3	 fax  compres-
       sion methods: MR	(Modified 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 partic-
       ular,  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.

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

	      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 op-

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

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

	      You cannot specify both -width and -paper_size.

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

	      This option tells	g3topbm	for what size paper this image is sup-
	      posed to be formatted.  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).

	      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.

       pbmtog3(1), tifftopnm(1), pbm(5)	fax formats(1)

       This manual page	was generated by the Netpbm tool 'makeman'  from  HTML
       source.	The master documentation is at

netpbm documentation	       03 December 2008		G3topbm	User Manual(0)


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