NAME
pbm - portable bitmap file format
DESCRIPTION
The portable bitmap format is a lowest common denominator
monochrome file format. It was originally designed to make
it reasonable to mail bitmaps between different types of
machines using the typical stupid network mailers we have
today. Now it serves as the common language of a large fam-
ily of bitmap conversion filters. The definition is as fol-
lows:
- A "magic number" for identifying the file type. A pbm
file's magic number is the two characters "P1".
- Whitespace (blanks, TABs, CRs, LFs).
- A width, formatted as ASCII characters in decimal.
- Whitespace.
- A height, again in ASCII decimal.
- Whitespace.
- Width * height bits, each either '1' or '0', starting at
the top-left corner of the bitmap, proceding in normal
English reading order.
- The character '1' means black, '0' means white.
- Whitespace in the bits section is ignored.
- Characters from a "#" to the next end-of-line are ignored
(comments).
- No line should be longer than 70 characters.
Here is an example of a small bitmap in this format:
P1
# feep.pbm
24 7
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 1 1 1 1 0 0 1 1 1 1 0 0 1 1 1 1 0 0 1 1 1 1 0
0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 1 0
0 1 1 1 0 0 0 1 1 1 0 0 0 1 1 1 0 0 0 1 1 1 1 0
0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0
0 1 0 0 0 0 0 1 1 1 1 0 0 1 1 1 1 0 0 1 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Programs that read this format should be as lenient as pos-
sible, accepting anything that looks remotely like a bitmap.
There is also a variant on the format, available by setting
the RAWBITS option at compile time. This variant is dif-
ferent in the following ways:
- The "magic number" is "P4" instead of "P1".
- The bits are stored eight per byte, high bit first low bit
last.
- No whitespace is allowed in the bits section.
- The files are eight times smaller and many times faster to
read and write.
SEE ALSO
brushtopbm(1), cmuwmtopbm(1), g3topbm(1), icontopbm(1), gem-
topbm(1), macptopbm(1), mgrtopbm(1), pbmlife(1), pbmmake(1),
pbmmask(1), pbmpaste(1), pbmreduce(1), pbmtoascii(1),
pbmtobbnbg(1), pbmtocmuwm(1), pbmtog3(1), pbmtogo(1),
pbmtoicon(1), pbmtolj(1), pbmtomacp(1), pbmtomgr(1),
pbmtoptx(1), pbmtorast(1), pbmtox10bm(1), pbmtoxbm(1),
pbmtoxwd(1), pbmupc(1), pcxtopbm(1), picttopbm(1), rast-
topbm(1), xbmtopbm(1), xwdtopbm(1), pnm(5), pgm(5), ppm(5)
AUTHOR
Copyright (C) 1989 by Jef Poskanzer.
Permission to use, copy, modify, and distribute this
software and its documentation for any purpose and without
fee is hereby granted, provided that the above copyright
notice appear in all copies and that both that copyright
notice and this permission notice appear in supporting docu-
mentation. This software is provided "as is" without
express or implied warranty.
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