pbm(5)                                                                  pbm(5)



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 family 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, proceeding 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 possible,
       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 different 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, and only a single char-
         acter  of  whitespace  (typically  a  newline)  is  allowed after the
         height.

       - The files are eight times smaller and many times faster to  read  and
         write.

SEE ALSO
       atktopbm(1),  brushtopbm(1),  cmuwmtopbm(1),  g3topbm(1),  gemtopbm(1),
       icontopbm(1), macptopbm(1), mgrtopbm(1), pi3topbm(1), xbmtopbm(1), ybm-
       topbm(1),  pbmto10x(1), pnmtoascii(1), pbmtoatk(1), pbmtobbnbg(1), pbm-
       tocmuwm(1), pbmtoepson(1), pbmtog3(1), pbmtogem(1), pbmtogo(1),  pbmto-
       icon(1),  pbmtolj(1),  pbmtomacp(1),  pbmtomgr(1),  pbmtopi3(1), pbmto-
       plot(1), pbmtoptx(1), pbmtox10bm(1), pbmtoxbm(1), pbmtoybm(1),  pbmtoz-
       inc(1),  pbmlife(1),  pbmmake(1), pbmmask(1), pbmreduce(1), pbmtext(1),
       pbmupc(1), pnm(5), pgm(5), ppm(5)

AUTHOR
       Copyright (C) 1989, 1991 by Jef Poskanzer.



                               27 September 1991                        pbm(5)
