pnm Functions
Updated: 22 July 2004
Table Of Contents
NAMElibpnm ‐ libnetpbm functions to read and write PNM image files
SYNOPSIS
#include <pnm.h>
void pnm_init( int *argcP, char *argv[] );
xel ** pnm_allocarray( int cols, int rows);
xel * pnm_allocrow( int cols);
void pnm_freearray( xel **xels, int rows);
void pnm_freerow( xel *xelrow);
void pnm_readpnminit( FILE *fp, int *colsP, int *rowsP, xelval
*maxvalP, int
*formatP );
void pnm_readpnmrow( FILE *fp, xel *xelrow, int cols,
xelval maxval, int format );
xel ** pnm_readpnm( FILE *fp, int *colsP, int *rowsP,
xelval *maxvalP, int* formatP );
void pnm_writepnminit( FILE * fp , int cols, int rows, xelval
maxval, int
format, int forceplain);
void pnm_writepnmrow( FILE *fp, xel *xelrow, int cols, xelval
maxval, int
format, int forceplain );
void pnm_writepnm( FILE *fp, xel ** xels, int cols, int rows,
xelval maxval,
int format, int forceplain );
void pnm_check( FILE * file, const enum pm_check_type
check_type, const int
format, const int cols, const int rows, const xelval max‐
val, enum
pm_check_code *retvalP);
void pnm_promoteformatrow( xel *xelrow, int cols, xelval max‐
val, int format,
xelval newmaxval, int newformat);
void pnm_promoteformat( xel **xels, int cols, xelval maxval,
int format,
xelval newmaxval, int newformat);
xel pnm_whitexel( xelval maxval, int format);
xel pnm_blackxel( xelval maxval, int format);
void pnm_invertxel( xel *x, xelval maxval, int format);
xel pnm_backgroundxelrow( xel *xelrow, int cols, xelval max‐
val, int format);
xel pnm_backgroundxel( xel **xels, int cols, int rows, xelval
maxval, int
format);
typedef ... xelval;
typedef ... xel;
extern xelval pnm_pbmmaxval;
#define PNM_ASSIGN1(x,v) ...
#define PNM_GET1(x) ...
#define PNM_EQUAL(x,y) ...
#define PNM_FORMAT_TYPE(format) ...
DESCRIPTION
These library functions are part of Netpbm.
PNM TYPES AND CONSTANTS
Each xel contains three xelvals, each of which should contain
only the
values between 0 and PNM_MAXMAXVAL, inclusive. pnm_pbmmaxval
is the maxval
used when a PNM program reads a PBM file. Normally it is 1;
however, for
some programs, a larger value gives better results.
PNM XEL MANIPULATIONS
The PNM_GET1 macro extracts a single value from an xel, when
you know it’s
from a PBM or PGM file. When it’s from a PPM file, use
PPM_GETR(),
PPM_GETG(), and PPM_GETB().
The PNM_ASSIGN1 macro assigns a single value to an xel, when
you know it’s
from a PBM or PGM file. When it’s from a PPM file, use PPM_AS‐
SIGN. The
PNM_EQUAL macro checks two xels for equality. The PNM_FOR‐
MAT_TYPE macro
computes a format type code from a format code. The format
types are PBM,
PGM, PPM, and PAM. But note that PBM, PGM, and PPM each are
two different
formats: a plain one and a raw one. So there are four format
types, but
seven formats. PNM_FORMAT_TYPE does not work on the PAM format
code.
INITIALIZATION
pnm_init is identical to pm_init().
MEMORY MANAGEMENT
pnm_allocarray() allocates space for an array of xels.
pnm_freearray() frees
an array space allocated by pnm_allocarray() or pnm_readpnm().
pnm_allocrow() allocates space for a row of a PNM image.
pnm_freerow() frees
it.
READING PNM FILES
pnm_readpnminit() is similar to pnm_readpaminit(), but reads
only PNM images
and has a different parameter list.
pnm_readpnmrow() is similar to pnm_readpamrow() but only works
on PNM images
and has a different parameter list and returns the row as an
array of xels
instead of tuples.
pnm_readpnm() is similar to pnm_readpam() except that it reads
only PNM
images and uses a different parameter list and returns an ar‐
ray of rows such
that pnm_readpnmrow() would return rather than such that
pnm_readpamrow()
would return.
WRITING FILES
pnm_writepnminit() is similar to pnm_writepaminit() except
that it can write
only a PNM header and has a different parameter list.
forceplain is a binary value. True (nonzero) means to write
the image in the
plain (ASCII) version of the selected format. False (zero)
means to write it
in the raw (binary) version of the selected format. See
PNM format
specification.
pnm_writepnmrow() is similar to pnm_writepamrow() except that
it works only
on PNM images and has a different parameter list and takes an
array of xels
instead of an array of tuples. See the description of force‐
plain above.pnm_writepnm() is similar to pnm_writepam() except that it
works only on PNM
image, has a different parameter list, and takes an array of
rows of xels
instead of an array of rows of tuples. See the description of
forceplain
above.
MISCELLANEOUS
pnm_check() is similar to pnm_checkpam() except it works only
on PNM images.pnm_check() is identical to ppm_check().
PNM FORMAT PROMOTION
pnm_promoteformatrow() promotes a row of xels from one maxval
and format to
a new set. Use this when you are combining multiple anymaps of
different
types ‐ just take the maximum of the maxvals and the maximum
of the formats,
and promote them all to that.
pnm_promoteformat() promotes an entire anymap.
PNM XEL MANIPULATION
pnm_whitexel() and pnm_blackxel() return a white or black xel,
respectively,
for the given maxval and format.
pnm_invertxel() inverts an xel.
pnm_backgroundxelrow() figures out an appropriate background
xel based on
the row of xels xelrow, which is cols xels wide, has maxval
maxval, and
represents an image with format format.
This estimate works best when the row is the top or bottom row
of the image.pnm_backgroundxel() does the same thing as pnm_backgroundxel‐
row(), except
based on an entire image instead of just one row. This tends
to do a
slightly better job than pnmbackgroundxelrow().
SEE ALSO
Libnetpbm, Libnetpbm User’s Guide, Libnetpbm Directory, pbm,
pgm, ppm, pam,
libpbm, libpgm, libppm
AUTHOR
Copyright (C) 1989, 1991 by Tony Hansen and Jef Poskanzer.
_________________________________________________________________
Table Of Contents
* NAME
* SYNOPSIS
* DESCRIPTION
+ PNM TYPES AND CONSTANTS
+ PNM XEL MANIPULATIONS
+ The
+ INITIALIZATION
+ MEMORY MANAGEMENT
+ READING PNM FILES
+ WRITING FILES
+ MISCELLANEOUS
+ PNM FORMAT PROMOTION
+ PNM XEL MANIPULATION
* SEE ALSO
* AUTHOR
