NAME

       libnetpbm - general introduction to the netpbm library

DESCRIPTION

       libnetpbm is a C programming library for reading, writing, and manipulating Netpbm images.
       It also contains a few general graphics manipulation tools, but it is not intended to be a
       graphics  tools  library.   For  graphics  tools,  Netpbm  expects  you  to run the Netpbm
       programs.  From a C program, the libnetpbm function pm_system() makes this easy.  However,
       since  it  creates  a  process  and  execs a program, this may be too heavyweight for some
       applications.

       To use libnetpbm services in your C program, #include the  pam.h  interface  header  file.
       For  historical  reasons,  you  can also get by in some cases with pbm.h, pgm.h, ppm.h, or
       pnm.h, but there's really no point to that anymore.

       The libnetpbm functions are divided into these categories:

       •      PBM functions.  These have names that start with pbm and work only on PBM images.

       •      PGM functions.  These have names that start with pgm and work only on PGM images.

       •      PPM functions.  These have names that start with ppm and work only on PPM images.

       •      PNM functions.  These have names that start with pnm and work on PBM, PGM, and  PPM
              images.

       •      PAM  functions.   These  also  have  names  that start with pnm and work on all the
              Netpbm image types.

       •      PM functions.  These are utility functions that aren't specific to  any  particular
              image format.

       For  new  programming, you rarely need to concern yourself with the PBM, PGM, PPM, and PNM
       functions, because the newer PAM functions do the same thing and are easier to  use.   For
       certain processing of bi-level images, the PBM functions are significantly more efficient,
       though.

       libnetpbm has a backward compatibility feature that means a function designed to read  one
       format  can  read  some others too, converting on the fly.  In particular, a function that
       reads a PGM image will also read a PBM image, but converts it as it reads it so  that  for
       programming  purposes,  it  is a PGM image.  Similarly, a function that reads PPM can read
       PBM and PGM as well.  And a function that reads PBM, PGM, or PPM can read a PAM  that  has
       an equivalent tuple type.

       For each of the five classes of libnetpbm image processing functions, libnetpbm has in in-
       memory representation for a pixel, a row, and a whole image.  Do not confuse  this  format
       with  the actual image format, as you would see in a file.  The libnetpbm in-memory format
       is designed to make programming very easy.  It is sometimes  extremely  inefficient,  even
       more  than the actual image format.  For example, a pixel that a PPM image represents with
       3 bytes, libnetpbm's PAM functions represent with 16 bytes.  A pixel in  a  PBM  image  is
       represented  by a single bit, but the PNM functions represent that pixel in memory with 96
       bits.

       See Libnetpbm User's Manual(1) for the basics on using libnetpbm in a program.

       You can look up the reference information for  a  particular  function  in  The  libnetpbm
       Directory(1).

       Before  Netpbm  release  10 (June 2002), this library was split into four: libpbm, libpgm,
       libppm, and libpnm.  That's largely the reason for the  multiple  sets  of  functions  and
       scattered documentation.

DOCUMENT SOURCE

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

              http://netpbm.sourceforge.net/doc/libnetpbm.html