TYPES AND CONSTANTS

typedef unsigned char gray;
#define PGM_MAXMAXVAL 255
extern gray pgm_pbmmaxval;

Each gray should contain only the values between 0 and PGM_MAXMAXVAL. 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 MEMORY MANAGEMENT

gray **pgm_allocarray(int cols, int rows)

Allocate an array of grays.

gray *pgm_allocrow( int cols )

Allocate a row of the given number of grays.

void pgm_freearray( grayrow, rows )

Free the array allocated with pgm_allocarray() containing the given number of rows.

pbm_freerow( grayrow )

Free a row of grays.

READING PBM FILES

void
pgm_readpgminit( file, colsP, rowsP, maxvalP, formatP )
FILE *file;
int *colsP, *rowsP, *formatP;
gray *maxvalP;

Read the header from a pgm file, filling in the rows, cols, maxval and format variables.

void
pgm_readpgmrow( file, grayrow, cols, maxval, format )
FILE *file;
gray *grayrow;
gray maxval;
int cols, format;

Read a row of grays into the grayrow array. Format and cols were filled in by pgm_readpgminit().

gray **
pgm_readpgm( file, colsP, rowsP, maxvalP )
FILE *file;
int *colsP, *rowsP;
gray *maxvalP;

Read an entire graymap file into memory, returning the allocated array and filling in the rows, cols and maxval variables. This function combines pgm_readpgminit(), pgm_allocarray() and pgm_readpgmrow().

WRITING PGM FILES

void
pgm_writepgminit( file, cols, rows, maxval )
FILE *file;
int cols, rows;
gray maxval;

Write the header for a portable graymap file.

void
pgm_writepgmrow( file, grayrow, cols, maxval )
FILE *file;
gray *grayrow;
int cols;
gray maxval;

Write a row from a portable graymap.

void
pgm_writepgm( file, bits, cols, rows, maxval )
FILE *file;
gray **bits;
int cols, rows;
gray maxval;

Write the header and all data for a portable graymap. This function combines pgm_writepgminit() and pgm_writepgmrow().