libpgm - functions to support portable graymap (PGM) programs
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 force-
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 retval);
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) ...
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; however, 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 for-
mat 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.
All PGM programs must call pgm_init() just after invocation, before they process their
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_allocarray() containing the given num-
ber of rows.
pgm_freerow() frees a row of grays allocated with pgm_allocrow().
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, returning 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().
pgm_writepgminit() writes the header for a PGM file and leaves it positioned just after
forceplain is a logical value that tells pgm_writepgminit() 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().
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.
libpbm(3), libppm(3), libpnm(3)