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       libpgm - functions to support portable graymap (PGM) programs


       #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 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) ...


       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 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.

       All  PGM  programs  must  call pgm_init() just after invocation, before
       they process their arguments.

       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 number 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 the header.

       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

       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_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


       libpbm(3), libppm(3), libpnm(3)