1Libnetpbm manual(3)        Library Functions Manual        Libnetpbm manual(3)
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NAME

6       libnetpbm - general introduction to the netpbm library
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DESCRIPTION

9       libnetpbm  is a C programming library for reading, writing, and manipu‐
10       lating Netpbm images.  It also contains a few general graphics  manipu‐
11       lation  tools,  but  it is not intended to be a graphics tools library.
12       For graphics tools, Netpbm expects you  to  run  the  Netpbm  programs.
13       From  a  C program, the libnetpbm function pm_system() makes this easy.
14       However, since it creates a process and execs a program,  this  may  be
15       too heavyweight for some applications.
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17       To  use libnetpbm services in your C program, #include the pam.h inter‐
18       face header file.  For historical reasons, you can also get by in  some
19       cases  with  pbm.h, pgm.h, ppm.h, or pnm.h, but there's really no point
20       to that anymore.
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22       The libnetpbm functions are divided into these categories:
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25       ·      PBM functions.  These have names that start with  pbm  and  work
26              only on PBM images.
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28       ·      PGM  functions.   These  have names that start with pgm and work
29              only on PGM images.
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31       ·      PPM functions.  These have names that start with  ppm  and  work
32              only on PPM images.
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34       ·      PNM functions.  These have names that start with pnm and work on
35              PBM, PGM, and PPM images.
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37       ·      PAM functions.  These also have names that start  with  pnm  and
38              work on all the Netpbm image types.
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40       ·      PM  functions.  These are utility functions that aren't specific
41              to any particular image format.
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44       For new programming, you rarely need to concern yourself with the  PBM,
45       PGM,  PPM,  and  PNM  functions, because the newer PAM functions do the
46       same thing and are easier to use.  For certain processing  of  bi-level
47       images, the PBM functions are significantly more efficient, though.
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49       libnetpbm  has  a  backward compatibility feature that means a function
50       designed to read one format can read some others too, converting on the
51       fly.  In particular, a function that reads a PGM image will also read a
52       PBM image, but converts it as it reads it so that for programming  pur‐
53       poses,  it  is  a  PGM image.  Similarly, a function that reads PPM can
54       read PBM and PGM as well.  And a function that reads PBM, PGM,  or  PPM
55       can read a PAM that has an equivalent tuple type.
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57       For  each  of the five classes of libnetpbm image processing functions,
58       libnetpbm has in in-memory representation for a pixel,  a  row,  and  a
59       whole  image.  Do not confuse this format with the actual image format,
60       as you would see in a file.  The libnetpbm in-memory format is designed
61       to  make programming very easy.  It is sometimes extremely inefficient,
62       even more than the actual image format.  For example, a  pixel  that  a
63       PPM  image represents with 3 bytes, libnetpbm's PAM functions represent
64       with 16 bytes.  A pixel in a PBM image is represented by a single  bit,
65       but the PNM functions represent that pixel in memory with 96 bits.
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67       See  LibnetpbmUser'sManual(1)forthe basics on using libnetpbm in a pro‐
68       gram.
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70       You can look up the reference information for a particular function  in
71       ThelibnetpbmDirectory(1).
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73       Before Netpbm release 10 (June 2002), this library was split into four:
74       libpbm, libpgm, libppm, and libpnm.  That's largely the reason for  the
75       multiple sets of functions and scattered documentation.
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79netpbm documentation             December 2003             Libnetpbm manual(3)