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User manual for old pgm functions
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pgm Functions
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Updated: 22 July 2004
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Table Of Contents
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NAME
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libpgm - libnetpbm functions to read and write PGM image files
.SH 2
SYNOPSIS
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\fB#include <pgm.h>\fR
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\fBvoid pgm_init( \fR
\fBint *\fR\fIargcP\fR\fB,\fR
\fBchar *\fR\fIargv\fR\fB[]\fR
\fB);\fR
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\fBgray ** pgm_allocarray(\fR
\fBint \fR\fIcols\fR\fB,\fR
\fBint \fR\fIrows\fR\fB );\fR
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\fBgray * pgm_allocrow(\fR
\fBint\fR\fIcols\fR\fB );\fR
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\fBvoid pgm_freearray(\fR
\fBgray **\fR\fIgrays\fR\fB,\fR
\fBint\fR\fIrows\fR\fB );\fR
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\fBvoid pgm_freerow(\fR
\fBgray *\fR\fIgrayrow\fR\fB);\fR
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\fBvoid pgm_readpgminit( \fR
\fBFILE *\fR\fIfp\fR\fB,\fR
\fBint *\fR\fIcolsP\fR\fB,\fR
\fBint *\fR\fIrowsP\fR\fB,\fR
\fBgray *\fR\fImaxvalP\fR\fB,\fR
\fBint *\fR\fIformatP\fR\fB );\fR
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\fBvoid pgm_readpgmrow( \fR
\fBFILE *\fR\fIfp\fR\fB,\fR
\fBgray *\fR\fIgrayrow\fR\fB,\fR
\fBint \fR\fIcols\fR\fB,\fR
\fBgray \fR\fImaxval\fR\fB,\fR
\fBint \fR\fIformat\fR\fB );\fR
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\fBgray ** pgm_readpgm( \fR
\fBFILE *\fR\fIfp\fR\fB,\fR
\fBint *\fR\fIcolsP\fR\fB,\fR
\fBint *\fR\fIrowsP\fR\fB,\fR
\fBgray *\fR\fImaxvalP\fR\fB );\fR
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\fBvoid pgm_writepgminit( \fR
\fBFILE *  fp , \fR
\fBint \fR\fIcols\fR\fB,\fR
\fBint \fR\fIrows\fR\fB,\fR
\fBgray \fR\fImaxval\fR\fB,\fR
\fBint \fR\fIforceplain\fR\fB );\fR
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\fBvoid pgm_writepgmrow( \fR
\fBFILE *\fR\fIfp\fR\fB,\fR
\fBgray *\fR\fIgrayrow\fR\fB,\fR
\fBint cols\fR\fI,\fR
\fBgray \fR\fImaxval\fR\fB,\fR
\fBint \fR\fIforceplain\fR\fB );\fR
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\fBvoid pgm_writepgm( \fR
\fBFILE *\fR\fIfp\fR\fB,\fR
\fBgray ** \fR\fIgrays\fR\fB,\fR
\fBint \fR\fIcols\fR\fB,\fR
\fBint \fR\fIrows\fR\fB,\fR
\fBgray \fR\fImaxval\fR\fB,\fR
\fBint \fR\fIforceplain\fR\fB );\fR
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\fBvoid pgm_writepgm( \fR
\fBFILE *\fR\fIfp\fR\fB,\fR
\fBgray **\fR\fIgrays\fR\fB,\fR
\fBint \fR\fIcols\fR\fB,\fR
\fBint \fR\fIrows\fR\fB,\fR
\fBgray \fR\fImaxval\fR\fB,\fR
\fBint \fR\fIforceplain\fR\fB );\fR
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\fBvoid pgm_nextimage(\fR
\fBFILE *\fR\fIfile\fR\fB,\fR
\fBint * const \fR\fIeofP\fR\fB);\fR
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\fBvoid pgm_check(\fR
\fBFILE * \fR\fIfile\fR\fB,\fR
\fBconst enum pm_check_type \fR\fIcheck_type\fR\fB,\fR
\fBconst int \fR\fIformat\fR\fB,\fR
\fBconst int \fR\fIcols\fR\fB,\fR
\fBconst int \fR\fIrows\fR\fB,\fR
\fBconst int \fR\fImaxval\fR\fB,\fR
\fBenum pm_check_code * const \fR\fIretval\fR\fB);\fR
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\fBtypedef ... gray;\fR
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\fB#define PGM_MAXMAXVAL ...\fR
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\fB#define PGM_OVERALLMAXVAL ...\fR
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\fBextern gray pgm_pbmmaxval;\fR
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\fB#define PGM_FORMAT ...\fR
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\fB#define RPGM_FORMAT ...\fR
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\fB#define PGM_TYPE PGM_FORMAT\fR
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\fB#define \fR
\fBPGM_FORMAT_TYPE(\fR\fIformat\fR\fB)\fR
\fB...\fR
.SH 2
DESCRIPTION
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These library functions are part of Netpbm.
.SH 3
TYPES AND CONSTANTS
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Each \fBgray\fR should contain only the values between \fB0\fR
and \fBPGM_OVERALLMAXVAL\fR.  \fBpgm_pbmmaxval\fR 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.
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\fBPGM_OVERALLMAXVAL\fR is the maximum value of a maxval in a PGM
file.  \fBPGM_MAXMAXVAL\fR 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 \fBPGM_MAXMAXVAL\fR cannot be read or
generated by old PGM processing programs and requires more file space.
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\fBPGM_FORMAT \fR is the format code for a Plain PGM format image
file.  \fBRPGM_FORMAT\fR is the format code for a Raw PGM format
image file.  \fBPGM_TYPE \fR is the format type code for the PGM
formats.  \fBPGM_FORMAT_TYPE\fR 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.
.SH 3
INITIALIZATION
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\fBpgm_init\fR is identical to \fBpm_init()\fR.
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MEMORY MANAGEMENT
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\fBpgm_allocarray()\fR allocates an array of grays.
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\fBpgm_allocrow()\fR allocates a row of the given number of grays.
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\fBpgm_freearray()\fR frees the array allocated with
\fBpgm_allocarray()\fR containing the given number of rows.
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\fBpgm_freerow()\fR frees a row of grays allocated with
\fBpgm_allocrow()\fR.
.SH 3
READING FILES
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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 \fIformat\fR value
returned by \fBpgm_readpgminit()\fR is, however, not translated.  It
represents the actual format of the PBM file.
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\fBpgm_readpgminit()\fR reads the header of a PGM file, returning
all the information from the header and leaving the file positioned
just after the header.
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\fBpgm_readpgmrow()\fR reads a row of grays into the \fIgrayrow
\fR array.  \fIformat\fR, \fIcols\fR, and \fImaxval \fR are the
values returned by \fBpgm_readpgminit()\fR.
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\fBpgm_readpgm()\fR reads an entire PGM image into memory,
returning the allocated array as its return value and returning the
information from the header as \fIrows\fR, \fIcols\fR, and
\fImaxval\fR.  This function combines \fBpgm_readpgminit()\fR,
\fBpgm_allocarray()\fR, and \fBpgm_readpgmrow()\fR.
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\fBpgm_readpgminit()\fR and \fBpgm_readpgm\fR abort the program with
a message to Standard Error if the PGM image header is not syntactically
valid, including if it contains a number too large to be processed using
the system's normal data structures (to wit, a number that won't fit in
a C 'int').
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WRITING FILES
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\fBpgm_writepgminit()\fR writes the header for a PGM file and leaves
it positioned just after the header.
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\fIforceplain\fR is a logical value that tells
\fBpgm_writepgminit() \fR to write a header for a plain PGM format
file, as opposed to a raw PGM format file.
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\fBpgm_writepgmrow()\fR writes the row \fIgrayrow\fR to a PGM
file.  For meaningful results, \fIcols\fR, \fImaxval\fR, and
\fIforceplain\fR must be the same as was used with
\fBpgm_writepgminit()\fR.
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\fBpgm_writepgm()\fR write the header and all data for a PGM
image.  This function combines \fBpgm_writepgminit()\fR and
\fBpgm_writepgmrow()\fR.
.SH 3
MISCELLANEOUS
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\fBpgm_nextimage()\fR positions a PGM input file to the next image
in it (so that a subsequent \fBpgm_readpgminit()\fR reads its
header).
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\fBpgm_nextimage()\fR is analogous to \fBpbm_nextimage()\fR, but
works on PGM and PBM files.
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\fBpgm_check() \fR checks for the common file integrity error
where the file is the wrong size to contain all the image data.
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\fBpgm_check() \fR is analogous to \fBpbm_check()\fR, but works
on PGM and PBM files.
.SH 2
SEE ALSO
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\fBlibpbm\fR,
\fBlibppm\fR,
\fBlibpnm\fR
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\l'5i'
.SH 2
Table Of Contents
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.IP \(bu
NAME
.IP \(bu
SYNOPSIS
.IP \(bu
DESCRIPTION
.IP \(bu
TYPES AND CONSTANTS
.IP \(bu
INITIALIZATION
.IP \(bu
MEMORY MANAGEMENT
.IP \(bu
READING FILES
.IP \(bu
WRITING FILES
.IP \(bu
MISCELLANEOUS
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.IP \(bu
SEE ALSO
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