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1 perry 1 rawtopgm
2 !!!rawtopgm
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 OPTIONS
7 SEE ALSO
8 AUTHORS
9 ----
10 !!NAME
11
12
13 rawtopgm - convert raw grayscale bytes into a portable graymap
14 !!SYNOPSIS
15
16
17 __rawtopgm__ [[__-bpp__ [[__1__|__2__]]
18 [[__-littleendian__] [[__-maxval__ ''N'']
19 [[__-headerskip__ ''N''] [[__-rowskip__ ''N'']
20 [[__-tb__|__-topbottom__] [[''width height'']
21 [[''imagefile'']
22 !!DESCRIPTION
23
24
25 Reads raw grayscale values as input. Produces a PGM file as
26 output. The input file is just a sequence of pure binary
27 numbers, either one or two bytes each, either bigendian or
28 littleendian, representing gray values. They may be arranged
29 either top to bottom, left to right or bottom to top, left
30 to right. There may be arbitrary header information at the
31 start of the file (to which __rawtopgm__ pays no
32 attention at all other than the header's size).
33
34
35 Arguments to __rawtopgm__ tell how to interpret the
36 pixels (a function that is served by a header in a regular
37 graphics format).
38
39
40 The ''width'' and ''height'' parameters tell the
41 dimensions of the image. If you omit these parameters,
42 __rawtopgm__ assumes it is a quadratic image and bases
43 the dimensions on the size of the input stream. If this size
44 is not a perfect square, __rawtopgm__ fails.
45
46
47 When you don't specify ''width'' and ''height'',
48 __rawtopgm__ reads the entire input stream into storage
49 at once, which may take a lot of storage. Otherwise,
50 __rawtopgm__ ordinarily stores only one row at a
51 time.
52
53
54 If you don't specify ''imagefile'', or specify __-__,
55 the input is from Standard Input.
56
57
58 The PGM output is to Standard Output.
59 !!OPTIONS
60
61
62 __-maxval__ ''N''
63
64
65 ''N'' is the maxval for the gray values in the input, and
66 is also the maxval of the PGM output image. The default is
67 the maximum value that can be represented in the number of
68 bytes used for each sample (i.e. 255 or 65535).
69
70
71 __-bpp__ [[__1__|__2__]
72
73
74 tells the number of bytes that represent each sample in the
75 input. If the value is __2__, The most significant byte
76 is first in the stream.
77
78
79 The default is 1 byte per sample.
80
81
82 __-littleendian__
83
84
85 says that the bytes of each input sample are ordered with
86 the least significant byte first. Without this option,
87 __rawtopgm__ assumes MSB first. This obviously has no
88 effect when there is only one byte per sample.
89
90
91 __-headerskip__ ''N''
92
93
94 __rawtopgm__ skips over ''N'' bytes at the beginning
95 of the stream and reads the image immediately after. The
96 default is 0.
97
98
99 This is useful when the input is actually some graphics
100 format that has a descriptive header followed by an ordinary
101 raster, and you don't have a program that understands the
102 header or you want to ignore the header.
103
104
105 __-rowskip__ ''N''
106
107
108 If there is padding at the ends of the rows, you can skip it
109 with this option. Note that rowskip need not be an integer.
110 Amazingly, I once had an image with 0.376 bytes of padding
111 per row. This turned out to be due to a file-transfer
112 problem, but I was still able to read the
113 image.
114
115
116 Skipping a fractional byte per row means skipping one byte
117 per multiple rows.
118
119
120 __-bt -bottomfirst__
121
122
123 By default, __rawtopgm__ assumes the pixels in the input
124 go top to bottom, left to right. If you specify __-bt__
125 or __-bottomfirst__, __rawtopgm__ assumes the pixels
126 go bottom to top, left to right. The Molecular Dynamics and
127 Leica confocal format, for example, use the latter
128 arrangement.
129
130
131 If you don't specify __-bt__ when you should or vice
132 versa, the resulting image is upside down, which you can
133 correct with __pnmflip .__
134
135
136 This option causes __rawtopgm__ to read the entire input
137 stream into storage at once, which may take a lot of
138 storage. Ordinarly, __rawtopgm__ stores only one row at a
139 time.
140
141
142 For backwards compatibility, __rawtopgm__ also accepts
143 __-tb__ and __-topbottom__ to mean exactly the same
144 thing. The reasons these are named backwards is that the
145 original author thought of it as specifying that the wrong
146 results of assuming the data is top to bottom should be
147 corrected by flipping the result top for bottom. Today, we
148 think of it as simply specifying the format of the input
149 data so that there are no wrong results.
150 !!SEE ALSO
151
152
153 pgm(5), rawtoppm(1),
154 pnmflip(1)
155 !!AUTHORS
156
157
158 Copyright (C) 1989 by Jef Poskanzer.
159 Modified June 1993 by Oliver Trepte,
160 oliver@fysik4.kth.se
161 ----
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