libpgm(3)libpgm(3)NAMElibpgm - functions to support portable graymap (PGM) pro
grams
SYNOPSIS
#include <pgm.h>
void pgm_init( int *argcP, char *argv[] );
gray ** pgm_allocarray( int cols, int rows );
gray * pgm_allocrow( intcols );
void pgm_freearray( gray **grays, introws );
void pgm_freerow( gray *grayrow);
void pgm_readpgminit( FILE *fp, int *colsP, int *rowsP,
gray *maxvalP, int *formatP );
void pgm_readpgmrow( FILE *fp, gray *grayrow, int cols,
gray maxval, int format );
gray ** pgm_readpgm( FILE *fp, int *colsP, int *rowsP,
gray *maxvalP );
void pgm_writepgminit( FILE * fp , int cols, int rows,
gray maxval, int forceplain );
void pgm_writepgmrow( FILE *fp, gray *grayrow, int cols,
gray maxval, int forceplain );
void pgm_writepgm( FILE *fp, gray ** grays, int cols, int
rows, gray maxval, int forceplain );
void pgm_writepgm( FILE *fp, gray **grays, int cols, int
rows, gray maxval, int forceplain );
void pgm_nextimage( FILE *file, int * const eofP);
void pgm_check( FILE * file, const enum pm_check_type
check_type, const int format, const int cols, const int
rows, const int maxval, enum pm_check_code * const ret_
val);
typedef ... gray;
#define PGM_MAXMAXVAL ...
#define PGM_OVERALLMAXVAL ...
extern gray pgm_pbmmaxval;
#define PGM_FORMAT ...
#define RPGM_FORMAT ...
#define PGM_TYPE PGM_FORMAT
#define PGM_FORMAT_TYPE(format) ...
DESCRIPTION
TYPES AND CONSTANTS
Each gray should contain only the values between 0 and
PGM_OVERALLMAXVAL. pgm_pbmmaxval is the maxval used when
a PGM program reads a PBM file. Normally it is 1; how
ever, for some programs, a larger value gives better
results.
PGM_OVERALLMAXVAL is the maximum value of a maxval in a
PGM file. PGM_MAXMAXVAL is the maximum value of a maxval
in a PGM file that is compatible with the PGM format as it
existed before April 2000. It is also the maximum value
of a maxval that results in the minimum possible raster
size for a particular image. I.e an image with a maxval
higher than PGM_MAXMAXVAL cannot be read or generated by
old PGM processing programs and requires more file space.
PGM_FORMAT is the format code for a Plain PGM format image
file. RPGM_FORMAT is the format code for a Raw PGM format
image file. PGM_TYPE is the format type code for the PGM
formats. PGM_FORMAT_TYPE is a macro that generates code
to compute the format type code of a PBM or PGM format
from the format code which is its argument.
INITIALIZATION
All PGM programs must call pgm_init() just after invoca
tion, before they process their arguments.
MEMORY MANAGEMENT
pgm_allocarray() allocates an array of grays.
pgm_allocrow() allocates a row of the given number of
grays.
pgm_freearray() frees the array allocated with pgm_allo
carray() containing the given number of rows.
pgm_freerow() frees a row of grays allocated with
pgm_allocrow().
READING FILES
If a function in this section is called on a PBM format
file, it translates the PBM file into a PGM file on the
fly and functions as if it were called on the equivalent
PGM file. The format value returned by pgm_readpgminit()
is, however, not translated. It represents the actual
format of the PBM file.
pgm_readpgminit() reads the header of a PGM file, return
ing all the information from the header and leaving the
file positioned just after the header.
pgm_readpgmrow() reads a row of grays into the grayrow
array. format, cols, and maxval are the values returned
by pgm_readpgminit().
pgm_readpgm() reads an entire PGM image into memory,
returning the allocated array as its return value and
returning the information from the header as rows, cols,
and maxval. This function combines pgm_readpgminit(),
pgm_allocarray(), and pgm_readpgmrow().
WRITING FILES
pgm_writepgminit() writes the header for a PGM file and
leaves it positioned just after the header.
forceplain is a logical value that tells pgm_writepg
minit() to write a header for a plain PGM format file, as
opposed to a raw PGM format file.
pgm_writepgmrow() writes the row grayrow to a PGM file.
For meaningful results, cols, maxval, and forceplain must
be the same as was used with pgm_writepgminit().
pgm_writepgm() write the header and all data for a PGM
image. This function combines pgm_writepgminit() and
pgm_writepgmrow().
MISCELLANEOUS
pgm_nextimage() positions a PGM input file to the next
image in it (so that a subsequent pgm_readpgminit() reads
its header).
pgm_nextimage() is analogous to pbm_nextimage(), but works
on PGM and PBM files.
pgm_check() checks for the common file integrity error
where the file is the wrong size to contain all the image
data.
pgm_check() is analogous to pbm_check(), but works on PGM
and PBM files.
SEE ALSOlibpbm(3), libppm(3), libpnm(3)libpgm(3)
