1Rawtopgm User Manual(0)                                Rawtopgm User Manual(0)
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NAME

6       rawtopgm - convert raw grayscale bytes to a PGM image
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SYNOPSIS

10       rawtopgm
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12       [-bpp [1|2]]
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14       [-littleendian]
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16       [-maxval N]
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18       [-headerskip N]
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20       [-rowskip N]
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22       [-tb|-topbottom]
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24       [width height]
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26       [imagefile]
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DESCRIPTION

30       This program is part of Netpbm(1).
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32       rawtopgm  reads  raw grayscale values as input and produces a PGM image
33       as output.  The input file is just a sequence of pure  binary  numbers,
34       either  one or two bytes each, either bigendian or littleendian, repre‐
35       senting gray values.  They may be arranged either top to  bottom,  left
36       to  right  or  bottom  to  top,  left to right.  There may be arbitrary
37       header information at the start of the file (to which rawtopgm pays  no
38       attention at all other than the header's size).
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40       Arguments to rawtopgm tell how to interpret the pixels (a function that
41       is served by a header in a regular graphics format).
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43       The width and height parameters tell the dimensions of the  image.   If
44       you omit these parameters, rawtopgm assumes it is a quadratic image and
45       bases the dimensions on the size of the input stream.  If this size  is
46       not a perfect square, rawtopgm fails.
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48       When  you  don't  specify  width  and height, rawtopgm reads the entire
49       input stream into storage at once, which may take  a  lot  of  storage.
50       Otherwise, rawtopgm ordinarily stores only one row at a time.
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52       If  you  don't specify imagefile, or specify -, the input is from Stan‐
53       dard Input.
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55       The PGM output is to Standard Output.
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OPTIONS

59       In addition to the options common to all programs  based  on  libnetpbm
60       (most notably -quiet, see
61        Common  Options  ⟨index.html#commonoptions⟩ ), rawtopgm recognizes the
62       following command line options:
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66       -maxval N
67              N is the maxval for the gray values in the input,  and  is  also
68              the  maxval of the PGM output image.  The default is the maximum
69              value that can be represented in the number of  bytes  used  for
70              each sample (i.e. 255 or 65535).
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73       -bpp [1|2]
74              tells  the  number  of  bytes  that represent each sample in the
75              input.  If the value is 2, The most significant byte is first in
76              the stream.
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78              The default is 1 byte per sample.
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81       -littleendian
82              says  that  the  bytes of each input sample are ordered with the
83              least significant byte first.   Without  this  option,  rawtopgm
84              assumes  MSB  first.  This obviously has no effect when there is
85              only one byte per sample.
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88       -headerskip N
89              rawtopgm skips over N bytes at the beginning of the  stream  and
90              reads the image immediately after.  The default is 0.
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92              This  is  useful when the input is actually some graphics format
93              that has a descriptive header followed by  an  ordinary  raster,
94              and  you don't have a program that understands the header or you
95              want to ignore the header.
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98       -rowskip N
99              If there is padding at the ends of the rows,  you  can  skip  it
100              with  this  option.   Note  that rowskip need not be an integer.
101              Amazingly, I once had an image with 0.376 bytes of  padding  per
102              row.   This turned out to be due to a file-transfer problem, but
103              I was still able to read the image.
104
105              Skipping a fractional byte per row means skipping one  byte  per
106              multiple rows.
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108
109       -bt -bottomfirst
110              By  default,  rawtopgm assumes the pixels in the input go top to
111              bottom, left to right.  If you specify -bt or -bottomfirst, raw‐
112              topgm  assumes  the pixels go bottom to top, left to right.  The
113              Molecular Dynamics and Leica confocal format, for  example,  use
114              the latter arrangement.
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116              If  you  don't  specify  -bt  when you should or vice versa, the
117              resulting image is upside down, which you can correct with  pam‐
118              flip.
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120              This option causes rawtopgm to read the entire input stream into
121              storage at once, which may take a  lot  of  storage.   Normally,
122              rawtopgm stores only one row at a time.
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124              For backwards compatibility, rawtopgm also accepts -tb
125               and  -topbottom  to  mean  exactly the same thing.  The reasons
126              these are named backwards is that the original author thought of
127              it  as specifying that the wrong results of assuming the data is
128              top to bottom should be corrected by flipping the result top for
129              bottom.   Today,  we think of it as simply specifying the format
130              of the input data so that there are no wrong results.
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SEE ALSO

136       pgm(1), rawtoppm(1), pamflip(1)
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AUTHORS

140       Copyright (C) 1989 by Jef Poskanzer.   Modified  June  1993  by  Oliver
141       Trepte, oliver@fysik4.kth.se
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DOCUMENT SOURCE

144       This  manual  page was generated by the Netpbm tool 'makeman' from HTML
145       source.  The master documentation is at
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147              http://netpbm.sourceforge.net/doc/rawtopgm.html
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149netpbm documentation           14 September 2000       Rawtopgm User Manual(0)