libpbm - functions to read and write PBM image files


SYNOPSIS

       #include <pbm.h>

       int pm_keymatch(char * str, char * keyword, int minchars);

       int pm_maxvaltobits(int maxval);

       int pm_bitstomaxval(int bits);

       unsigned  int  pm_lcm(unsigned  int  x,  unsigned  int  y,
       unsigned int z, unsigned int limit);

       void pm_message(char * fmt, ... );

       void pm_error(char * fmt, ... );

       void pm_perror(char * fmt, ... );

       void pm_usage(char * usage);

       FILE *pm_openr(char * name)

       FILE *pm_openw(char * name);

       FILE *pm_close(FILE * fp);

       char *pm_read_unknown_size(FILE * fp, long *nread);

       bit **pbm_allocarray(int cols,  int rows);

       bit *pbm_allocrow(int cols);

       pbm_freearray(bit **bits, int rows);

       pbm_freerow(bit *bitrow);

       void  pbm_readpbminit(FILE  *  fp, int *colsP, int *rowsP,
       int *formatP);

       void pbm_readpbmrow(FILE * fp, bit *bitrow, int cols,  int
       format);

       void pbm_readpbmrow_packed(FILE * fp,
       unsigned  char  * const packed_bits, const int cols, const
       int format);

       void bit** pbm_readpbm(FILE * fp, int *colsP, int *rowsP);

       void  pbm_writepbminit(FILE  * fp, int cols, int rows, int
       forceplain);

       forceplain);

       void pbm_writepbmrow_packed(FILE * fp,
       unsigned  char  * const packed_bits, const int cols, const
       int forceplain);

       void pbm_writepbm(FILE * fp, bit  **bits,  int  cols,  int
       rows, int forceplain);

       #define pbm_packed_bytes(cols) ...

       void pbm_nextimage( FILE *file, int * const eofP);

       void  pbm_check(  FILE  *  file,  const enum pm_check_type
       check_type, const int format, const int  cols,  const  int
       rows, enum pm_check_code * const retval);

       int pm_readbigshort(FILE *in, short *sP);

       int pm_writebigshort(FILE *out, short s);

       int pm_readbiglong(FILE *in, long *lP);

       int pm_writebiglong(FILE *out, long l);

       int pm_readlittleshort(FILE *in, short *sP);

       int pm_writelittleshort(FILE *out, short s);

       int pm_readlittlelong(FILE *in, long *lP);

       int pm_writelittlelong(FILE *out, long l);


DESCRIPTION - PACKAGE-WIDE ROUTINES

   KEYWORD MATCHING
       pm_keymatch() does a case-insensitive match of str against
       keyword.  str can be a leading sunstring of  keyword,  but
       at least minchars must be present.

   MAXVAL ARITHMETIC
       pm_maxvaltobits()  and pm_bitstomaxval() convert between a
       maxval and the minimum number of bits required to hold it.

       pm_lcm() computes the least common multiple of 3 integers.
       You also specify a limit and if the LCM  would  be  higher
       than that limit, pm_lcm() just returns that limit.

       pm_message()  is  a  printf()  style  routine  to write an
       informational message to the Standard Error  file  stream.
       pm_message()  suppresses the message, however, if the user
       specified the -quiet option on the command line.  See  the
       initialization  functions,  e.g.  pbm_init(), for informa­
       tion on the -quiet option.  Note that Netpbm programs  are
       often used interactively, but also often used by programs.
       In the interactive case, it  is  nice  to  issue  messages
       about  what the program is doing, but in the program case,
       such messages are usually undesirable.  By  using  pm_mes­
       sage() for all your messages, you make your program usable
       in both cases.  Without any effort on your  part,  program
       users of your program can avoid the messages by specifying
       the -quiet option.

       pm_error() is a printf()  style  routine  that  writes  an
       error  message to the Standard Error file stream and exits
       the program with an exit code of 1.

   GENERIC FILE ACCESS
       pm_openr() opens the given file for reading,  with  appro­
       priate  error  checking.  A filename of - is taken to mean
       Standard Input.  pm_openw() opens the given file for writ­
       ing,  with  appropriate error checking.  pm_close() closes
       the file  descriptor,  with  appropriate  error  checking.
       pm_read_unknown_size()  reads  an  entire  file  or  input
       stream of unknown size to a buffer.  Allocate memory  more
       memory  as  needed.  The  calling  routine has to free the
       allocated buffer with free().

       pm_read_unknown_size() returns a pointer to the  allocated
       buffer.  The  nread  argument  returns the number of bytes
       read.

   ENDIAN I/O
       pm_readbigshort(),  pm_writebigshort(),  pm_readbiglong(),
       pm_writebiglong(),    pm_readlittleshort(),   pm_writelit­
       tleshort(), pm_readlittlelong(), and  pm_writelittlelong()
       are  routines  to  read  and  write short and long ints in
       either big- or little-endian byte order.  The return value
       is  0  upon success and -1 upon failure (either EOF or I/O
       error).


DESCRIPTION - PBM-SPECIFIC ROUTINES

   TYPES AND CONSTANTS
       typedef ... bit;

       #define PBM_WHITE ...

       #define PBM_BLACK ...

       PBM_BLACK.

       #define PBM_FORMAT ...

       #define RPBM_FORMAT ...

       #define PBM_TYPE PBM_FORMAT

       #define PBM_FORMAT_TYPE(f) ...

       These  are  for  distinguishing different file formats and
       types.

   INITIALIZATION
       All PBM programs must call pbm_init just after invocation,
       before processing arguments.

   MEMORY MANAGEMENT
       pbm_allocarray()    allocates    an    array    of   bits.
       pbm_allocrow() allocates a row  of  the  given  number  of
       bits.   pbm_freearray()  frees  the  array  allocated with
       pbm_allocarray() containing  the  given  number  of  rows.
       pbm_freerow() frees a row of bits.

   READING PBM IMAGE FILES
       pbm_readpbminit()  reads  the header from a PBM image in a
       PBM file, filling in the rows, cols and format  variables.
       pbm_readpbmrow()  reads  a  row  of  bits  into the bitrow
       array.  Format and cols  were  filled  in  by  pbm_readpb­
       minit().   pbm_readpbmrow_packed()  is  like pbm_readrow()
       except instead of returning a bits array,  it  returns  an
       array  packed_bits  of  bytes with the pixels of the image
       row packed into them.  The pixels are in order  from  left
       to  right  across  the  row  and from the beginning of the
       array to the end.  Within a byte, the bits  are  in  order
       from  the  most  significant  bit to the least significant
       bit.  If the number of pixels in the row is not a multiple
       of 8, the last byte returned is padded on the least signf­
       icant bit side with undefined bits.  White is  represented
       by a PBM_WHITE bit; black by PBM_BLACK.

       pbm_readpbm()  reads  an  entire  bitmap file into memory,
       returning the allocated array and filling in the rows  and
       cols variables.  This function combines pbm_readpbminit(),
       pbm_allocarray() and pbm_readpbmrow().

   WRITING PBM IMAGE FILES
       pbm_writepbminit() writes the header for a PBM image in  a
       PBM file.  forceplain is a boolean value specifying that a

       raw  format  (binary) one.  pbm_writepbmrow() writes a row
       to a PBM file.  pbm_writepbmrow_packed() is  the  same  as
       pbm_writepbmrow()  except that you supply the row to write
       as an array of bytes packed with bits instead of as a bits
       array.   The  format  of  packed_bits  is the same as that
       returned by pbm_readpbmrow().

       pbm_writepbm() writes the header and all data  for  a  PBM
       image  to a PBM file.  This function combines pbm_writepb­
       minit() and pbm_writepbmrow().

   MISCELLANEOUS
       pbm_nextimage() positions a PBM input  file  to  the  next
       image  in it (so that a subsequent pbm_readpbminit() reads
       its header).

       Immediately before a call  to  pbm_nextimage(),  the  file
       must  be  positioned either at its beginning (i.e. nothing
       has been read from the file yet) or just  after  an  image
       (i.e. as left by a pbm_readpbmrow() of the last row in the
       image).

       In effect, then, all pbm_nextimage() does is test  whether
       there is a next image or the file is positioned at end-of-
       file.

       If pbm_nextimage()  successfully  positions  to  the  next
       image,  it  returns  *eofP false (0).  If there is no next
       image in the file, it returns *eofP true (1).  If it can't
       position or determine the file status due to a file error,
       it issues an error message and exits the program  with  an
       error exit code.

       pbm_check()  checks  for  the  common file integrity error
       where the file is the wrong size to contain all the  image
       data.  pbm_check() assumes the file is positioned after an
       image header (as if pbm_readpbminit() was the last  opera­
       tion  on the file).  It checks the file size to see if the
       number of bytes left in the file are the  number  required
       to  contain  the  image raster.  If the file is too short,
       pbm_check() causes the program to exit with an error  mes­
       sage and error completion code.  Otherwise, it returns one
       of  the  following  values  (enumerations  of   the   enum
       pm_check_code type) as *retval:

       PM_CHECK_OK
              The file's size is exactly what is required to hold
              the image raster.

       PM_CHECK_UNKNOWN_TYPE
              format is not a format whose size  pbm_check()  can
              anticipate.  The only format with which pbm_check()


       PM_CHECK_TOO_LONG
              The file is longer than it needs to be  to  contain
              the  image raster.  The extra data might be another
              image.

       PM_CHECK_UNCHECKABLE
              The file is not a kind that has a predictable size,
              so  there  is no simple way for pbm_check() to know
              if it is the right size.  Only a regular  file  has
              predictable  size.  A pipe is a common example of a
              file that does not.

       check_type must have the value PM_CHECK_BASIC (an  enumer­
       ated  value of the pm_check_type enumerated type).  Other­
       wise, the effect of pbm_check()  is  unpredictable.   This
       argument  exists  for future backward compatible expansion
       of the function of pbm_check().


SEE ALSO

       libpgm(3), libppm(3), libpnm(3), pbm(5)


AUTHOR

       Copyright (C) 1989, 1991 by Tony Hansen and Jef Poskanzer.


Man(1) output converted with man2html