Provided by: netpbm_10.97.00-2_amd64 bug


       pbm - Netpbm bi-level image format


       This program is part of Netpbm(1).

       The  PBM  format  is a lowest common denominator monochrome file format.  It serves as the
       common language of a large family of bitmap image conversion filters.  Because the  format
       pays  no  heed  to efficiency, it is simple and general enough that one can easily develop
       programs to convert to and from just about any other graphics format, or to manipulate the

       The name "PBM" is an acronym derived from "Portable Bit Map."

       This  is  not  a  format  that one would normally use to store a file or to transmit it to
       someone -- it's  too  expensive  and  not  expressive  enough  for  that.   It's  just  an
       intermediary  format.   In  it's  purest  use,  it  lives only in a pipe between two other


       The format definition is as follows.

       A PBM file consists of a  sequence  of  one  or  more  PBM  images.  There  are  no  data,
       delimiters, or padding before, after, or between images.

       Each PBM image consists of the following:

       •      A  "magic number" for identifying the file type.  A pbm image's magic number is the
              two characters "P4".

       •      Whitespace (blanks, TABs, CRs, LFs).

       •      The width in pixels of the image, formatted as ASCII characters in decimal.

       •      Whitespace.

       •      The height in pixels of the image, again in ASCII decimal.

       •      A single whitespace character (usually a newline).

       •      A raster of Height rows, in order from top to bottom.   Each  row  is  Width  bits,
              packed  8  to  a  byte,  with don't care bits to fill out the last byte in the row.
              Each bit represents a pixel: 1 is black, 0 is white.  The order of  the  pixels  is
              left  to  right.   The  order  of  their  storage  within  each  file  byte is most
              significant bit to least significant bit.  The order of the file bytes is from  the
              beginning of the file toward the end of the file.

              A  row  of  an image is horizontal.  A column is vertical.  The pixels in the image
              are square and contiguous.

       •      Before the whitespace character that delimits the raster, any characters from a "#"
              through the next carriage return or newline character, is a comment and is ignored.
              Note that this is rather unconventional, because a comment can actually be  in  the
              middle of what you might consider a token.  Note also that this means if you have a
              comment right before the raster, the newline at the  end  of  the  comment  is  not
              sufficient to delimit the raster.

       All characters referred to herein are encoded in ASCII.  "newline" refers to the character
       known in ASCII as Line Feed or LF.  A "white space" character is space, CR, LF,  TAB,  VT,
       or FF (I.e. what the ANSI standard C isspace() function calls white space).

   Plain PBM
       There  is  actually another version of the PBM format, even more simplistic, more lavishly
       wasteful of space than PBM, called Plain PBM.  Plain PBM actually came first, but even its
       inventor  couldn't  stand  its  recklessly  squanderous use of resources after a while and
       switched to what we now know as the regular PBM format.  But Plain PBM is so redundant  --
       so  overstated  --  that  it's virtually impossible to break.  You can send it through the
       most liberal mail system (which was the original purpose of the PBM format)  and  it  will
       arrive  still  readable.   You can flip a dozen random bits and easily piece back together
       the original image.  And we hardly need to define the format here, because you can  decode
       it by inspection.

       Netpbm  programs  generate  Raw PBM format instead of Plain PBM by default, but the common
       option ⟨index.html#commonoptions⟩  -plain chooses Plain PBM.

       The difference is:


              There is exactly one image in a file.


              The "magic number" is "P1" instead of "P4".


              Each pixel in the raster is represented by a byte  containing  ASCII  '1'  or  '0',
              representing  black and white respectively.  There are no fill bits at the end of a


              White space in the raster section is ignored.


              You can put any junk you want after the raster, if it starts  with  a  white  space


              No line should be longer than 70 characters.

              Here is an example of a small image in the plain PBM format.
              # 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

       There is a newline character at the end of each of these lines.

       You can generate the Plain PBM format from the regular PBM format (first image in the file
       only) with the pnmtoplainpnm program.

       Programs that read this format should be as lenient as possible, accepting  anything  that
       looks remotely like a bitmap.


       No  Internet  Media  Type  (aka  MIME type, content type) for PBM has been registered with
       IANA, but the value image/x-portable-bitmap is conventional.

       Note that the PNM Internet Media Type image/x-portable-anymap also applies.


       There are no requirements on the name of a PBM file, but the  convention  is  to  use  the
       suffix  ".pbm".   "pnm"  is  also conventional, for cases where distinguishing between the
       particular subformats of PNM is not convenient.


       Before July 2000, there could be at most one image in a PBM file.  As a result, most tools
       to process PBM files ignore (and don't read) any data after the first image.


       libnetpbm(1), pnm(1), pgm(1), ppm(1), pam(1), programs that process PBM(1)


       This  manual page was generated by the Netpbm tool 'makeman' from HTML source.  The master
       documentation is at