Penguin
Recent Changes
Annotated edit history of pbm(5) version 1, including all changes. View license author blame.
Rev Author # Line
1 perry 1 pbm
2 !!!pbm
3 NAME
4 DESCRIPTION
5 COMPATIBILITY
6 SEE ALSO
7 AUTHOR
8 ----
9 !!NAME
10
11
12 pbm - portable bitmap file format
13 !!DESCRIPTION
14
15
16 The portable bitmap format is a lowest common denominator
17 monochrome file format. It serves as the common language of
18 a large family of bitmap conversion filters. Because the
19 format pays no heed to efficiency, it is simple and general
20 enough that one can easily develop programs to convert to
21 and from just about any other graphics format, or to
22 manipulate the image.
23
24
25 This is not a format that one would normally use to store a
26 file or to transmit it to someone -- it's too expensive and
27 not expressive enough for that. It's just an intermediary
28 format. In it's purest use, it lives only in a pipe between
29 two other programs.
30
31
32 The format definition is as follows.
33
34
35 A PBM file consists of a sequence of one or more PBM images.
36 There are no data, delimiters, or padding before, after, or
37 between images.
38
39
40 Each PBM image consists of the following:
41
42
43 -
44
45
46 A
47
48
49 -
50
51
52 Whitespace (blanks, TABs, CRs, LFs).
53
54
55 -
56
57
58 The width in pixels of the image, formatted as ASCII
59 characters in decimal.
60
61
62 -
63
64
65 Whitespace.
66
67
68 -
69
70
71 The height in pixels of the image, again in ASCII
72 decimal.
73
74
75 -
76
77
78 Newline or other single whitespace character.
79
80
81 -
82
83
84 A raster of Height rows, in order from top to bottom. Each
85 row is Width bits, packed 8 to a byte, with don't care bits
86 to fill out the last byte in the row. Each bit represents a
87 pixel: 1 is black, 0 is white. The order of the pixels is
88 left to right. The order of their storage within each file
89 byte is most significant bit to least significant bit. The
90 order of the file bytes is from the beginning of the file
91 toward the end of the file.
92
93
94 -
95
96
97 Characters from a
98
99
100 There is actually another version of the PBM format, even
101 more more simplistic, more lavishly wasteful of space than
102 PBM, called Plain PBM. Plain PBM actually came first, but
103 even its inventor couldn't stand its recklessly squanderous
104 use of resources after a while and switched to what we now
105 know as the regular PBM format. But Plain PBM is so
106 redundant -- so overstated -- that it's virtually impossible
107 to break. You can send it through the most liberal mail
108 system (which was the original purpose of the PBM format)
109 and it will arrive still readable. You can flip a dozen
110 random bits and easily piece back together the original
111 image. And we hardly need to define the format here, because
112 you can decode it by inspection.
113
114
115 The difference is:
116
117
118 -
119
120
121 There is exactly one image in a file.
122
123
124 -
125
126
127 The
128
129
130 -
131
132
133 Each pixel in the raster is represented by a byte containing
134 ASCII '1' or '0', representing black and white respectively.
135 There are no fill bits at the end of a row.
136
137
138 -
139
140
141 White space in the raster section is ignored.
142
143
144 -
145
146
147 You can put any junk you want after the raster, if it starts
148 with a white space character.
149
150
151 -
152
153
154 No line should be longer than 70 characters.
155
156
157 Here is an example of a small bitmap in the plain PBM
158 format:
159
160
161 P1
162 # feep.pbm
163 24 7
164 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
165 0 1 1 1 1 0 0 1 1 1 1 0 0 1 1 1 1 0 0 1 1 1 1 0
166 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 1 0
167 0 1 1 1 0 0 0 1 1 1 0 0 0 1 1 1 0 0 0 1 1 1 1 0
168 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0
169 0 1 0 0 0 0 0 1 1 1 1 0 0 1 1 1 1 0 0 1 0 0 0 0
170 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
171 You can generate the Plain PBM format from the regular PBM format (first image in the file only) with the __pnmtoplainpnm__ program.
172
173
174 Programs that read this format should be as lenient as
175 possible, accepting anything that looks remotely like a
176 bitmap.
177 !!COMPATIBILITY
178
179
180 Before July 2000, there could be at most one image in a PBM
181 file. As a result, most tools to process PBM files ignore
182 (and don't read) any data after the first
183 image.
184 !!SEE ALSO
185
186
187 libpbm(3),pnm(5),pgm(5),ppm(5)
188 !!AUTHOR
189
190
191 Copyright (C) 1989, 1991 by Jef Poskanzer.
192 ----
This page is a man page (or other imported legacy content). We are unable to automatically determine the license status of this page.