Libnetpbm manual(3) Libnetpbm manual(3)NAMElibnetpbm - general introduction to the netpbm library
DESCRIPTIONlibnetpbm is a C programming library for reading, writing, and manipu‐
lating Netpbm images. It also contains a few general graphics manipu‐
lation 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 inter‐
face 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 pur‐
poses, 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 LibnetpbmUser'sManual(1)
for the basics on using libnetpbm in a program.
You can look up the reference information for a particular function in
ThelibnetpbmDirectory(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.
netpbm documentation December 2003 Libnetpbm manual(3)