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| author | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2006-12-25 03:06:05 +0000 |
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| committer | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2006-12-25 03:06:05 +0000 |
| commit | 1017cbebe5d5edd859e0fddad0a8600f509f4821 (patch) | |
| tree | 78bdf336648566f7a7d55f42837357dea3dd674c /g3topbm.html | |
| parent | 16f2ac126651015a376eba864a3a35f738b0b25a (diff) | |
| download | netpbm-mirror-1017cbebe5d5edd859e0fddad0a8600f509f4821.tar.gz netpbm-mirror-1017cbebe5d5edd859e0fddad0a8600f509f4821.tar.xz netpbm-mirror-1017cbebe5d5edd859e0fddad0a8600f509f4821.zip | |
Place user guide into Subversion repository
git-svn-id: http://svn.code.sf.net/p/netpbm/code/userguide@181 9d0c8265-081b-0410-96cb-a4ca84ce46f8
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1 files changed, 144 insertions, 0 deletions
diff --git a/g3topbm.html b/g3topbm.html new file mode 100644 index 00000000..e04ed5b8 --- /dev/null +++ b/g3topbm.html @@ -0,0 +1,144 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2//EN"> +<HTML><HEAD><TITLE>G3topbm User Manual</TITLE></HEAD> +<BODY> +<H1>g3topbm</H1> +Updated: 28 February 2006 +<BR> +<A HREF="#index">Table Of Contents</A> + +<H2>NAME</H2> +g3topbm - convert a Group 3 fax file into a PBM image + +<H2 id="synopsis">SYNOPSIS</H2> + +<B>g3topbm</B> +[<B>-kludge</B>] +[<B>-reversebits</B>] +[<B>-stretch</B>] +[{<B>-width=</B><i>pixels</i> | paper_size={A3,A4,A5,A6,B4}] +[<B>-stop_error</B>] +[<I>g3file</I>] + +<p>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. + +<H2 id="description">DESCRIPTION</H2> + +<p>This program is part of <a href="index.html">Netpbm</a>. + +<p><b>g3topbm</b> reads a Group 3 fax file as input and produces a PBM +image as output. + +<p><b>g3topbm</b> 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; <b>g3topbm</b> 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. + +<p>You can use the <b>stop_error</b> option to make <b>g3topbm</b> +insist on valid input. + +<H2 id="options">OPTIONS</H2> + +<DL COMPACT> +<DT><B>-kludge</B> + +<DD>Tells <b>g3topbm</b> to ignore the first few lines of the file; +sometimes fax files have some junk at the beginning. + +<DT><B>-reversebits</B> + +<DD>Tells <b>g3topbm</b> 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. + +<DT><B>-stretch</B> + +<DD>This option tells <b>g3topbm</b> to stretch the image vertically by +duplicating each row. This is for the low-quality transmission mode. + +<dt><b>-width=</b><i>pixels</i> + +<dd>This option tells <b>g3topbm</b> that the image is supposed to be +<i>pixels</i> pixels wide. If any line in it is not that size, <b>g3topbm</b> +issues a warning or fails, depending on whether you specify +<b>-stop_error</b>. + +<p>You cannot specify both <b>-width</b> and <b>-paper_size</b>. + +<p>This option was new in Netpbm 10.33 (March 2006). + +<dt><b>-paper_size=</b>{<B>A3</B>,<B>A4</B>,<B>A5</B>,<b>A6</b>,<b>B4</b>} + +<dd>This option tells <b>g3topbm</b> for what size paper this image is +supposed to be formatted. <b>g3topbm</b> uses the width of the paper +the same way as with the <b>-width</b> option. <b>g3topbm</b> +does not use the height of the paper for anything. + +<p>You cannot specify both <b>-width</b> and <b>-paper_size</b>. + +<p>This option was new in Netpbm 10.33 (March 2006). + +<DT><B>-stop_error</B> + +<DD>This option tells <b>g3topbm</b> 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. + +<p>If you don't specify this option, <b>g3topbm</b> 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, +<b>g3topbm</b> produces output containing the lines up to where it +encountered the problem. + +<p><b>g3topbm</b> issues warning messages when it continues in spite of +input errors. + +<p>This option was new in Netpbm 10.24 (August 2004). Before that, +<b>g3topbm</b> always failed when it encountered premature EOF and +never failed when it encountered other problems. + +</DL> + +<H2 id="g3">ABOUT G3</H2> + +<P>G3 is the near universal format used by fax machines. There is also +a newer, more capable G4. + +<p>The standard for Group 3 fax is defined in CCITT Recommendation T.4. +In the U.S., that is implemented by EIA standards EIA-465 and EIA-466. +These standards cover the layers below the image format (which are +irrelevant to <b>g3topbm</b> as well. + +<p>G3 faxes are 204 dots per inch (dpi) horizontally and 98 dpi (196 +dpi optionally, in fine-detail mode) vertically. Since G3 neither +assumes error free transmission nor retransmits when errors occur, the +encoding scheme used is differential only over small segments never +exceeding 2 lines at standard resolution or 4 lines for fine-detail. +(The incremental G3 encoding scheme is called two-dimensional and the +number of lines so encoded is specified by a parameter called k.) + + +<H2 id="seealso">SEE ALSO</H2> + +<A HREF="pbmtog3.html">pbmtog3</A>, +<A HREF="pbm.html">pbm</A> + +<HR> +<H2 id="index">Table Of Contents</H2> +<UL> +<LI><A HREF="#synopsis">SYNOPSIS</A> +<LI><A HREF="#description">DESCRIPTION</A> +<LI><A HREF="#options">OPTIONS</A> +<LI><A HREF="#g3">ABOUT G3</A> +<LI><A HREF="#seealso">SEE ALSO</A> +</UL> +</BODY> +</HTML> |