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libpgm(3)


NAME

   libpgm - functions to support portable graymap (PGM) programs

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_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) ...

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;  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.

   INITIALIZATION
   All  PGM  programs  must  call pgm_init() just after invocation, 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_allocarray()
   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, 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().

   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_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().

   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 ALSO

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

                                                                 libpgm(3)



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