1PBMTOJBG(1)                 General Commands Manual                PBMTOJBG(1)
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NAME

6       pbmtojbg - portable bitmap to JBIG1 file converter
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SYNOPSIS

9       pbmtojbg [ options ] [ input-file | -  [ output-file ]]
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DESCRIPTION

12       Reads  in  a  portable bitmap (PBM) from a file or standard input, com‐
13       presses it, and outputs the image as  a  JBIG1  bi-level  image  entity
14       (BIE) file.
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16       JBIG1 is a highly effective lossless compression algorithm for bi-level
17       images (one bit per pixel), which is particularly suitable for  scanned
18       document pages.
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20       A JBIG1 encoded image can be stored in several resolutions (progressive
21       mode).  These resolution layers can be stored all in one single BIE  or
22       they  can be stored in several separate BIE files.  All resolution lay‐
23       ers except the lowest one are stored merely as differences to the  next
24       lower  resolution layer, because this requires less space than encoding
25       the full image completely every time. Each resolution layer  has  twice
26       the number of horizontal and vertical pixels than the next lower layer.
27       JBIG1 files can also store several bits per pixel  as  separate  bitmap
28       planes, and pbmtojbg can read a PGM file and transform it into a multi-
29       bitplane BIE.
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OPTIONS

33       -             A single hyphen instead of an input file name will  cause
34                     pbmtojbg  to  read  the  data from standard input instead
35                     from a file.
36
37       -q            Encode the image in one single resolution layer  (sequen‐
38                     tial  mode).  This is usually the most efficient compres‐
39                     sion method. By default, the number of resolution  layers
40                     is  chosen automatically such that the lowest layer image
41                     is not larger than 640 × 480 pixels. This is  a  shortcut
42                     for -d 0.
43
44       -x number     Specify the maximal horizontal size of the lowest resolu‐
45                     tion layer.  The default is 640 pixels.
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47       -y number     Specify the maximal vertical size of the  lowest  resolu‐
48                     tion layer.  The default is 480 pixels.
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50       -l number     Select  the  lowest resolution layer that will be written
51                     to the BIE. It is possible to store the  various  resolu‐
52                     tion  layers  of  a  JBIG1 image in progressive mode into
53                     different BIEs. Options -l and -h  allow  to  select  the
54                     resolution-layer interval that will appear in the created
55                     BIE. The lowest resolution layer has number 0 and this is
56                     also  the  default  value.  By default all layers will be
57                     written.
58
59       -h number     Select the highest resolution layer that will be  written
60                     to  the  BIE.  By default all layers will be written. See
61                     also option -l.
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63       -b            Use binary values instead of Gray code words in order  to
64                     encode  pixel  values  in multiple bitplanes. This option
65                     has only an effect if the input is a PGM file and if more
66                     than  one bitplane is produced. Note that the decoder has
67                     to make the same selection but cannot determine from  the
68                     BIE,  whether  Gray or binary code words were used by the
69                     encoder.
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71       -d number     Specify the total number of differential resolution  lay‐
72                     ers  into which the input image will be split in addition
73                     to the lowest layer. Each additional  layer  reduces  the
74                     size of layer 0 by 50 %. This option overrides options -x
75                     and -y which  are  usually  a  more  comfortable  way  of
76                     selecting the number of resolution layers.
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78       -s number     The  JBIG1  algorithm  splits each image into a number of
79                     horizontal  stripes.  This  option  specifies  that  each
80                     stripe  shall  have  number lines in layer 0. The default
81                     value is selected so that approximately 35  stripes  will
82                     be used for the whole image.
83
84       -m number     Select the maximum horizontal offset of the adaptive tem‐
85                     plate pixel.  The JBIG1 encoder uses ten neighbour pixels
86                     to estimate the probability of the next pixel being black
87                     or white. It can move one out of these ten  pixels.  This
88                     is  especially useful for dithered images, as long as the
89                     distance of this adaptive pixel can be  adjusted  to  the
90                     period  of  the  dither pattern. By default, the adaptive
91                     template pixel is allowed to move up  to  8  pixels  away
92                     horizontally.  This  encoder supports distances up to 127
93                     pixels. Annex A of the standard  suggests  that  decoders
94                     should  support at least a horizontal distance of 16 pix‐
95                     els, so using values not higher than 16 for number  might
96                     increase the chances of interoperability with other JBIG1
97                     implementations. On the other hand, the T.85 fax applica‐
98                     tion profile requires decoders to support horizontal off‐
99                     sets up to 127 pixels, which the maximum value  permitted
100                     by  the  standard.  (The  maximal  vertical offset of the
101                     adaptive template pixel is always zero for this encoder.)
102
103       -t number     Encode only the specified number of most significant  bit
104                     planes.  This  option  allows  to  reduce the depth of an
105                     input PGM file if not all bits per pixel  are  needed  in
106                     the output.
107
108       -o number     JBIG1 separates an image into several horizontal stripes,
109                     resolution layers and planes, were  each  plane  contains
110                     one  bit  per  pixel.  One single stripe in one plane and
111                     layer is encoded as a data unit called stripe data entity
112                     (SDE)  inside  the  BIE.  There are 12 different possible
113                     orders in which the SDEs can be stored inside the BIE and
114                     number  selects which one shall be used. The order of the
115                     SDEs is only  relevant  for  applications  that  want  to
116                     decode  a JBIG1 file which has not yet completely arrived
117                     from e.g. a slow network connection.  For  instance  some
118                     applications prefer that the outermost of the three loops
119                     (stripes, layers, planes) is over all layers so that  all
120                     data of the lowest resolution layer is transmitted first.
121                     The   following  values  for  number  select  these  loop
122                     arrangements for writing the SDEs (outermost loop first):
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124                        0      planes, layers, stripes
125                        2      layers, planes, stripes
126                        3      layers, stripes, planes
127                        4      stripes, planes, layers
128                        5      planes, stripes, layers
129                        6      stripes, layers, planes
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131                     All loops count starting with zero, however by  adding  8
132                     to  the  above order code, the layer loop can be reversed
133                     so that it counts down to zero and then higher resolution
134                     layers will be stored before lower layers.  Default order
135                     is 3 which writes at first all planes of the first stripe
136                     and  then  completes  layer  0 before continuing with the
137                     next layer and so on.
138
139       -p number     This option allows  to  activate  or  deactivate  various
140                     optional  algorithms  defined in the JBIG1 standard. Just
141                     add the numbers of the following options which  you  want
142                     to activate in order to get the number value:
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144                        4      deterministic prediction (DPON)
145                        8      layer 0 typical prediction (TPBON)
146                       16      diff. layer typ. pred. (TPDON)
147                       64      layer 0 two-line template (LRLTWO)
148
149                     Except  for special applications (like communication with
150                     JBIG1 subset implementations) and for debugging  purposes
151                     you  will  normally not want to change anything here. The
152                     default  is  28,  which  provides  the  best  compression
153                     result.
154
155       -C string     Add  the  string  in a comment marker segment to the pro‐
156                     duced data stream. (There is no support  at  present  for
157                     adding comments that contain the zero byte.)
158
159       -c            Determine  the  adaptive  template pixel movement as sug‐
160                     gested in annex C of the standard. By  default  the  tem‐
161                     plate change takes place directly in the next line, which
162                     is most effective. However, a few conformance test  exam‐
163                     ples in the standard require the adaptive template change
164                     to be delayed until the first line of  the  next  stripe.
165                     This  option selects this special behavior, which is nor‐
166                     mally not required except in order to pass  some  confor‐
167                     mance tests.
168
169       -r            Use the SDRST marker instead of the normal SDNORM marker.
170                     The probably only useful application of this option is to
171                     generate  test  data for checking whether a JBIG1 decoder
172                     has implemented SDRST correctly. In a normal  JBIG1  data
173                     stream, each stripe data entity (SDE) is terminated by an
174                     SDNORM marker, which preserves the state  of  the  arith‐
175                     metic  encoder (and more) for the next stripe in the same
176                     layer. The alternative SDRST marker resets this state  at
177                     the end of the stripe.
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179       -Y number     A  long  time  ago, there were fax machines that couldn't
180                     even hold a single page in  memory.  They  had  to  start
181                     transmitting  data  before  the  page was scanned in com‐
182                     pletely and the length  of  the  image  was  known.   The
183                     authors  of  the standard added a rather ugly hack to the
184                     otherwise beautiful JBIG1 format  to  support  this.  The
185                     NEWLEN  marker  segment  can  override  the  image height
186                     stated in the BIE  header  anywhere  later  in  the  data
187                     stream.  Normally  pbmtojbg never generates NEWLEN marker
188                     segments, as it knows the correct image  height  when  it
189                     outputs  the  header.  This option is solely intended for
190                     the purpose of generating test files with  NEWLEN  marker
191                     segments.  It  can  be  used  to specify a higher initial
192                     image height for use in the BIE header, and pbmtojbg will
193                     then  add  a NEWLEN marker segment at the latest possible
194                     opportunity to the data  stream  to  signal  the  correct
195                     final height.
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197       -f            This  option makes the output file comply to the "facsim‐
198                     ile application profile" defined in ITU-T  Recommendation
199                     T.85.  It  is  a shortcut for -q -o 0 -p 8 -s 128 -t 1 -m
200                     127.
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202       -v            After the BIE has been created, a few  technical  details
203                     of the created file will be listed (verbose mode).
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BUGS

206       Using  standard input and standard output for binary data works only on
207       systems where there is no difference between binary  and  text  streams
208       (e.g.,  Unix). On other systems (e.g., MS-DOS), using standard input or
209       standard output may cause control  characters  like  CR  or  LF  to  be
210       inserted or deleted and this will damage the binary data.
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STANDARDS

213       This  program  implements the JBIG1 image coding algorithm as specified
214       in ISO/IEC 11544:1993 and ITU-T T.82(1993).
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AUTHOR

217       The pbmtojbg program is part of the JBIG-KIT package,  which  has  been
218       developed  by  Markus  Kuhn.   The most recent version of this portable
219       JBIG1    library    and     tools     set     is     available     from
220       <http://www.cl.cam.ac.uk/~mgk25/jbigkit/>.
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SEE ALSO

223       pbm(5), pgm(5), jbgtopbm(1)
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227                                  2003-06-04                       PBMTOJBG(1)
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