1Rawtopgm User Manual(0)                                Rawtopgm User Manual(0)
2
3
4

NAME

6       rawtopgm - convert raw grayscale bytes to a PGM image
7
8

SYNOPSIS

10       rawtopgm
11
12       [-bpp [1|2]]
13
14       [-littleendian]
15
16       [-maxval N]
17
18       [-headerskip N]
19
20       [-rowskip N]
21
22       [-tb|-topbottom]
23
24       [width height]
25
26       [imagefile]
27
28

DESCRIPTION

30       This program is part of Netpbm(1).
31
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).
39
40       Arguments to rawtopgm tell how to interpret the pixels (a function that
41       is served by a header in a regular graphics format).
42
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.
47
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.
51
52       If  you  don't specify imagefile, or specify -, the input is from Stan‐
53       dard Input.
54
55       The PGM output is to Standard Output.
56
57

OPTIONS

59       -maxval N
60              N is the maxval for the gray values in the input,  and  is  also
61              the  maxval of the PGM output image.  The default is the maximum
62              value that can be represented in the number of  bytes  used  for
63              each sample (i.e. 255 or 65535).
64
65
66       -bpp [1|2]
67              tells  the  number  of  bytes  that represent each sample in the
68              input.  If the value is 2, The most significant byte is first in
69              the stream.
70
71              The default is 1 byte per sample.
72
73
74       -littleendian
75              says  that  the  bytes of each input sample are ordered with the
76              least significant byte first.   Without  this  option,  rawtopgm
77              assumes  MSB  first.  This obviously has no effect when there is
78              only one byte per sample.
79
80
81       -headerskip N
82              rawtopgm skips over N bytes at the beginning of the  stream  and
83              reads the image immediately after.  The default is 0.
84
85              This  is  useful when the input is actually some graphics format
86              that has a descriptive header followed by  an  ordinary  raster,
87              and  you don't have a program that understands the header or you
88              want to ignore the header.
89
90
91       -rowskip N
92              If there is padding at the ends of the rows,  you  can  skip  it
93              with  this  option.   Note  that rowskip need not be an integer.
94              Amazingly, I once had an image with 0.376 bytes of  padding  per
95              row.   This turned out to be due to a file-transfer problem, but
96              I was still able to read the image.
97
98              Skipping a fractional byte per row means skipping one  byte  per
99              multiple rows.
100
101
102       -bt -bottomfirst
103              By  default,  rawtopgm assumes the pixels in the input go top to
104              bottom, left to right.  If you specify -bt or -bottomfirst, raw‐
105              topgm  assumes  the pixels go bottom to top, left to right.  The
106              Molecular Dynamics and Leica confocal format, for  example,  use
107              the latter arrangement.
108
109              If  you  don't  specify  -bt  when you should or vice versa, the
110              resulting image is upside down, which you can correct with  pam‐
111              flip.
112
113              This option causes rawtopgm to read the entire input stream into
114              storage at once, which may take a  lot  of  storage.   Normally,
115              rawtopgm stores only one row at a time.
116
117              For backwards compatibility, rawtopgm also accepts -tb
118               and  -topbottom  to  mean  exactly the same thing.  The reasons
119              these are named backwards is that the original author thought of
120              it  as specifying that the wrong results of assuming the data is
121              top to bottom should be corrected by flipping the result top for
122              bottom.   Today,  we think of it as simply specifying the format
123              of the input data so that there are no wrong results.
124
125
126
127

SEE ALSO

129       pgm(1), rawtoppm(1), pamflip(1)
130
131

AUTHORS

133       Copyright (C) 1989 by Jef Poskanzer.   Modified  June  1993  by  Oliver
134       Trepte, oliver@fysik4.kth.se
135

DOCUMENT SOURCE

137       This  manual  page was generated by the Netpbm tool 'makeman' from HTML
138       source.  The master documentation is at
139
140              http://netpbm.sourceforge.net/doc/rawtopgm.html
141
142netpbm documentation           14 September 2000       Rawtopgm User Manual(0)