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.TH pgm 3
.SH NAME
pgm - functions to support portable graymap programs
.SH SYNOPSIS
.Ss
#include <pgm.h>
cc ... libpgm.a libpbm.a
.Se
.SH DESCRIPTION
.SS TYPES AND CONSTANTS
.Ss
typedef unsigned char gray;
#define PGM_MAXMAXVAL 255
extern gray pgm_pbmmaxval;
.Se
Each
.IR gray
should contain only the values between
.IR 0
and
.IR PGM_MAXMAXVAL .
.IR pgm_pbmmaxval
is the maxval used when a PGM program reads a PBM file.
Normally it is 1; however, for some programs, a larger value gives better
results.
.SS PGM MEMORY MANAGEMENT
.Ss
gray **pgm_allocarray(int cols, int rows)
.Se
Allocate an array of grays.
.Ss
gray *pgm_allocrow( int cols )
.Se
Allocate a row of the given number of grays.
.Ss
void pgm_freearray( grayrow, rows )
.Se
Free the array allocated with
.IR pgm_allocarray()
containing the given number
of rows.
.Ss
pbm_freerow( grayrow )
.Se
Free a row of grays.
.SS READING PBM FILES
.Ss
void
pgm_readpgminit( file, colsP, rowsP, maxvalP, formatP )
FILE *file;
int *colsP, *rowsP, *formatP;
gray *maxvalP;
.Se
Read the header from a pgm file, filling in the rows, cols, maxval and format
variables.
.Ss
void
pgm_readpgmrow( file, grayrow, cols, maxval, format )
FILE *file;
gray *grayrow;
gray maxval;
int cols, format;
.Se
Read a row of grays into the grayrow array.
Format and cols were filled in by
.IR pgm_readpgminit() .
.Ss
gray **
pgm_readpgm( file, colsP, rowsP, maxvalP )
FILE *file;
int *colsP, *rowsP;
gray *maxvalP;
.Se
Read an entire graymap file into memory, returning the allocated array and
filling in the rows, cols and maxval variables.
This function combines
.IR pgm_readpgminit() ,
.IR pgm_allocarray()
and
.IR pgm_readpgmrow() .
.SS WRITING PGM FILES
.Ss
void
pgm_writepgminit( file, cols, rows, maxval )
FILE *file;
int cols, rows;
gray maxval;
.Se
Write the header for a portable graymap file.
.Ss
void
pgm_writepgmrow( file, grayrow, cols, maxval )
FILE *file;
gray *grayrow;
int cols;
gray maxval;
.Se
Write a row from a portable graymap.
.Ss
void
pgm_writepgm( file, bits, cols, rows, maxval )
FILE *file;
gray **bits;
int cols, rows;
gray maxval;
.Se
Write the header and all data for a portable graymap.
This function combines
.IR pgm_writepgminit()
and
.IR pgm_writepgmrow() .
.SH "SEE ALSO"
pgm(3), ppm(3)
.SH AUTHOR
Manual by Tony Hansen.

Copyright (C) 1989 by Jef Poskanzer.

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation.  This software is provided "as is" without express or
implied warranty.