.TH libpbm 3
.SH NAME
libpbm - functions to read and write PBM image files
.SH SYNOPSIS
.B #include <pbm.h>

.B int pm_keymatch(char * 
.IB str , 
.B char * 
.IB keyword , 
.B int 
.IB minchars );

.B int pm_maxvaltobits(int
.IB maxval );

.B int pm_bitstomaxval(int
.IB bits );

.B unsigned int pm_lcm(unsigned int
.IB x ,
.B unsigned int
.IB y ,
.B unsigned int
.IB z ,
.B unsigned int
.IB limit );

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

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

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

.B void pm_usage(char *
.IB usage );

.B FILE *pm_openr(char *
.IB name )

.B FILE *pm_openw(char *
.IB name );

.B FILE *pm_openr_seekable(const char *
.IB name );

.B FILE *pm_close(FILE *
.IB fp );

.B char *pm_read_unknown_size(FILE *
.IB fp ", long *" nread );

.B unsigned int pm_tell(FILE * 
.IB fileP );

.B void pm_seek(FILE * 
.IB fileP ", unsigned long " filepos );

.B bit **pbm_allocarray(int
.IB cols ",  int " rows );

.B bit *pbm_allocrow(int
.IB cols );

.B pbm_freearray(bit 
.BI ** bits ", int " rows );

.B pbm_freerow(bit
.BI * bitrow );

.B void pbm_readpbminit(FILE *
.IB fp ", int *" colsP ", int *" rowsP ", int *" formatP );

.B void pbm_readpbmrow(FILE *
.IB fp ", bit *" bitrow ", int " cols ", int " format );

.B void pbm_readpbmrow_packed(FILE *
.IB fp , 
.br
.BI "unsigned char * const " packed_bits ,
.BI "const int " cols ,
.BI "const int " format );

.B void bit** pbm_readpbm(FILE *
.IB fp ", int *" colsP ", int *" rowsP );

.B void pbm_writepbminit(FILE *
.IB fp ", int " cols ", int " rows ", int " forceplain );

.B void pbm_writepbmrow(FILE *
.IB fp ", bit *" bitrow ", int " cols ", int " forceplain );

.B void pbm_writepbmrow_packed(FILE *
.IB fp , 
.br
.BI "unsigned char * const " packed_bits ,
.BI "const int " cols ,
.BI "const int " forceplain );

.B void pbm_writepbm(FILE *
.IB fp ", bit **" bits ", int " cols ", int " rows ", int " forceplain );

.BI "#define pbm_packed_bytes(" cols ") ..."

.B void pbm_nextimage(
.BI "FILE *" file ,
.BI "int * const " eofP );

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

.BI "int pm_readbigshort(FILE *" in ", short *" sP );

.BI "int pm_writebigshort(FILE *" out ", short " s );

.BI "int pm_readbiglong(FILE *" in ", long *" lP );

.BI "int pm_writebiglong(FILE *" out ", long " l );

.BI "int pm_readlittleshort(FILE *" in ", short *" sP );

.BI "int pm_writelittleshort(FILE *" out ", short " s );

.BI "int pm_readlittlelong(FILE *" in ", long *" lP );

.BI "int pm_writelittlelong(FILE *" out ", long " l );


.SH DESCRIPTION - PACKAGE-WIDE ROUTINES

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

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

.B 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,
.B pm_lcm()
just returns that limit.


.SS MESSAGES AND ERRORS
.B pm_message()
is a
.BR printf()
style routine to write an informational message to the Standard Error
file stream.
.B pm_message()
suppresses the message, however, if the user specified the
.B -quiet
option on the command line.  See the initialization functions, e.g.
.BR pbm_init() ,
for information on the 
.B -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 
.B pm_message()
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 
.B -quiet
option.

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

.SS GENERIC FILE ACCESS
.B pm_openr()
opens the given file for reading, with appropriate error checking.
A filename of 
.B - 
is taken to mean Standard Input.
.B pm_openw()
opens the given file for writing, with appropriate error checking.
.B pm_close()
closes the file descriptor, with appropriate error checking.

.B pm_openr_seekable()
appears to open the file just like 
.BR pm_openr() ,
but the file thus opened is guaranteed to be seekable (you can use
ftell() and fseek() on it).  
.B pm_openr_seekable() 
pulls this off by copying the entire file to a temporary file and
giving you the handle of the temporary file, if it has to.  If the 
file you name is a regular file, it's already seekable so 
.B pm_openr_seekable()
just does the same thing as
.BR pm_openr() .
But if it is, say, a pipe, it isn't seekable.  So 
.B pm_openr_seekable()
reads the pipe until EOF into a temporary file, then opens that temporary
file and returns the handle of the temporary file.  The temporary file is
seekable.  

The file
.B pm_openr_seekable()
creates is one that the operating system recognizes as temporary, so
when you close the file, by any means, it gets deleted.

You need a seekable file if you intend to make multiple passes through
the file.  The only alternative is to read the entire image into
memory and work from that copy.  That may use too much memory.  Note
that the image takes less space in the file cache than in a buffer in
memory.  As much as 96 times less space!  Each sample is an integer in
the buffer, which is usually 96 bits.  In the file, a sample may be as
small as 1 bit and rarely more than 8 bits.

.B 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
.BR free() .

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

.BR pm_tell() 
returns a handle for the current position of the file, whether it be
the header or a row of the raster.  Use the handle as an argument to
.B pm_seek()
to reposition the file there later.  The file must be seekable (which 
you can ensure by opening it with
.BR pm_openr_seekable() ) or this may fail.

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

.SH DESCRIPTION - PBM-SPECIFIC ROUTINES

.SS TYPES AND CONSTANTS
.B typedef ... bit;

.B #define PBM_WHITE ...

.B #define PBM_BLACK ...

Each
.BR bit
should contain only the values of
.BR PBM_WHITE
or
.BR PBM_BLACK .

.B #define PBM_FORMAT ...

.B #define RPBM_FORMAT ...

.B #define PBM_TYPE PBM_FORMAT

.B #define 
.BI PBM_FORMAT_TYPE( f ") ..."

These are for distinguishing different file formats and types.

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

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

.SS READING PBM IMAGE FILES
.B pbm_readpbminit()
reads the header from a PBM image in a PBM file, filling in the rows,
cols and format variables.
.B pbm_readpbmrow()
reads a row of bits into the 
.I bitrow 
array.  Format and cols were filled in by
.BR pbm_readpbminit() .
.B pbm_readpbmrow_packed()
is like 
.B pbm_readrow()
except instead of returning a 
.B bits
array, it returns an array 
.I 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 signficant bit side with undefined
bits.  White is represented by a
.B PBM_WHITE
bit; black by
.BR PBM_BLACK .

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

.SS WRITING PBM IMAGE FILES
.B pbm_writepbminit()
writes the header for a PBM image in a PBM file.  
.I forceplain
is a boolean value specifying that a plain format (text) file to be
written, as opposed to a raw format (binary) one.
.B pbm_writepbmrow()
writes a row to a PBM file.
.B pbm_writepbmrow_packed()
is the same as 
.B pbm_writepbmrow()
except that you supply the row to write as an array of bytes packed with
bits instead of as a 
.B bits
array.  The format of
.I packed_bits 
is the same as that returned by 
.BR pbm_readpbmrow() .

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

.SS MISCELLANEOUS

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

Immediately before a call to 
.BR 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
.B pbm_readpbmrow() 
of the last row in the image).

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

If 
.B pbm_nextimage() 
successfully positions to the next image, it returns 
.BI * eofP
false (0).  If there is no next image in the file, it returns
.BI * 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.

.B pbm_check()
checks for the common file integrity error where the file is the wrong
size to contain all the image data.
.B pbm_check() 
assumes the file is positioned after an image header (as if
.B pbm_readpbminit() 
was the last operation 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, 
.B pbm_check()
causes the program to exit with an error message and error completion
code.  Otherwise, it returns one of the following values (enumerations
of the
.B enum pm_check_code
type) as 
.BI * retval\fR:
.TP
.B PM_CHECK_OK
The file's size is exactly what is required to hold the image raster.
.TP
.B PM_CHECK_UNKNOWN_TYPE
.I format
is not a format whose size 
.B pbm_check()
can anticipate.  The only format with which 
.B pbm_check()
can deal is raw PBM format.
.TP
.B 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.
.TP
.B PM_CHECK_UNCHECKABLE
The file is not a kind that has a predictable size, so there is no simple
way for 
.B 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.

.PP
.I check_type
must have the value
.B PM_CHECK_BASIC 
(an enumerated value of the 
.B pm_check_type
enumerated type).  Otherwise, the effect of
.B pbm_check()
is unpredictable.  This argument exists for future backward compatible
expansion of the function of
.BR pbm_check() .


.SH "SEE ALSO"
.BR libpgm (3), 
.BR libppm (3), 
.BR libpnm (3), 
.BR pbm (5)
.SH AUTHOR
Copyright (C) 1989, 1991 by Tony Hansen and Jef Poskanzer.
.\" Permission to use, copy, modify, and distribute this software and its
.\" documentation for any purpose and without fee is hereby granted, provided
.\" that the above copyright notice appear in all copies and that both that
.\" copyright notice and this permission notice appear in supporting
.\" documentation.  This software is provided "as is" without express or
.\" implied warranty.