1G3topbm User Manual(0) G3topbm User Manual(0)
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6 g3topbm - convert a Group 3 fax file into a PBM image
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10 g3topbm [-kludge] [-reversebits] [-stretch] [-width=pixels |
11 paper_size={A3|A4|A5|A6|B4}] [-stop_error] [g3file]
12 Minimum unique abbreviation of option is acceptable. You may use dou‐
14 ble hyphens instead of single hyphen to denote options. You may use
15 white space in place of the equals sign to separate an option name from
16 its value.
17
20 This program is part of Netpbm(1).
21 g3topbm reads a Group 3 fax file with MH (Modified Huffman) compression
23 as input and produces a PBM image as output.
24 g3topbm tolerates various deviations from the standard, so as to
26 recover some of the image if there was a transmission error. One thing
27 it tolerates is lines of varying length. The standard requires all the
28 lines to be the same length; g3topbm makes the output image as wide as
29 the longest line in the input and pads the others on the right. It
30 warns you when it does this.
31 You can use the stop_error option to make g3topbm insist on valid
33 input.
34 There is no Netpbm program that understands the other G3 fax compres‐
36 sion methods: MR (Modified Read) and MMR (Modified Modified Read).
37 Note that the Group 3 fax file format does not include any kind of a
39 signature so that g3topbm might verify it's actually looking at a G3
40 file or that the compression method is MH. The program will interpret
41 any sequence of bytes you give it as if it is G3 and, while typically
42 issuing a lot of error messages about the file not conforming to the G3
43 MH format, will produce output (unless you use -stoperror). In partic‐
44 ular, if you feed g3topbm an MR or MMR file, it will not tell you of
45 your mistake.
46 There are subformats of TIFF that use the Group 3 fax encodings inside.
48 See tifftopnm.
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53 -kludge
54 Tells g3topbm to ignore the first few lines of the file; some‐
55 times fax files have some junk at the beginning.
56 -reversebits
59 Tells g3topbm to interpret bits least-significant first, instead
60 of the default most-significant first. Apparently some fax
61 modems do it one way and others do it the other way. If you get
62 a whole bunch of "bad code word" messages, try using this
63 option.
64 -stretch
67 This option tells g3topbm to stretch the image vertically by
68 duplicating each row. This is for the low-quality transmission
69 mode.
70 -width=pixels
73 This option tells g3topbm that the image is supposed to be pix‐
74 els pixels wide. If any line in it is not that size, g3topbm
75 issues a warning or fails, depending on whether you specify
76 -stop_error.
77 You cannot specify both -width and -paper_size.
79 This option was new in Netpbm 10.33 (March 2006).
81 -paper_size={A3,A4,A5,A6,B4}
84 This option tells g3topbm for what size paper this image is sup‐
85 posed to be formatted. g3topbm uses the width of the paper the
86 same way as with the -width option. g3topbm does not use the
87 height of the paper for anything.
88 You cannot specify both -width and -paper_size.
90 This option was new in Netpbm 10.33 (March 2006).
92 -stop_error
95 This option tells g3topbm to fail when it finds a problem in the
96 input. "Fail" means it terminates with a nonzero status code
97 with the contents of the output file undefined.
98 If you don't specify this option, g3topbm does its best to work
100 around input errors and salvage as much of the image as possible
101 in the output image. It first tries to resynchronize to a later
102 line by searching for the next End Of Line marker, skipping any
103 lines or partial lines in between. It saves the beginning of
104 the line in which it encountered the problem. If the input file
105 ends prematurely, g3topbm produces output containing the lines
106 up to where it encountered the problem.
107 g3topbm issues warning messages when it continues in spite of
109 input errors.
110 This option was new in Netpbm 10.24 (August 2004). Before that,
112 g3topbm always failed when it encountered premature EOF and
113 never failed when it encountered other problems.
114
120 pbmtog3(1), tifftopnm(1), pbm(1) fax formats(1)
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123 This manual page was generated by the Netpbm tool 'makeman' from HTML
124 source. The master documentation is at
125 http://netpbm.sourceforge.net/doc/g3topbm.html
127netpbm documentation 03 December 2008 G3topbm User Manual(0)