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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.3//EN">
<html>
<head>
<title>User manual for old pgm functions</title>
<meta name="manual_section" content="3">
</head>
<body>
<h1>pgm Functions</h1>
Updated: 08 September 2007
<br>
<a href="#index">Table Of Contents</a>
<h2>NAME</h2>
libpgm - libnetpbm functions to read and write PGM image files
<h2 id="synopsis">SYNOPSIS</h2>
<b>#include <netpbm/pgm.h></b>
<p>
<b>void pgm_init( </b>
<b>int *</b><i>argcP</i><b>,</b>
<b>char *</b><i>argv</i><b>[]</b>
<b>);</b>
<p>
<b>gray ** pgm_allocarray(</b>
<b>int </b><i>cols</i><b>,</b>
<b>int </b><i>rows</i><b> );</b>
<p>
<b>gray * pgm_allocrow(</b>
<b>int</b><i>cols</i><b> );</b>
<p>
<b>void pgm_freearray(</b>
<b>gray **</b><i>grays</i><b>,</b>
<b>int</b><i>rows</i><b> );</b>
<p>
<b>void pgm_freerow(</b>
<b>gray *</b><i>grayrow</i><b>);</b>
<p>
<b>void pgm_readpgminit( </b>
<b>FILE *</b><i>fp</i><b>,</b>
<b>int *</b><i>colsP</i><b>,</b>
<b>int *</b><i>rowsP</i><b>,</b>
<b>gray *</b><i>maxvalP</i><b>,</b>
<b>int *</b><i>formatP</i><b> );</b>
<p>
<b>void pgm_readpgmrow( </b>
<b>FILE *</b><i>fp</i><b>,</b>
<b>gray *</b><i>grayrow</i><b>,</b>
<b>int </b><i>cols</i><b>,</b>
<b>gray </b><i>maxval</i><b>,</b>
<b>int </b><i>format</i><b> );</b>
<p>
<b>gray ** pgm_readpgm( </b>
<b>FILE *</b><i>fp</i><b>,</b>
<b>int *</b><i>colsP</i><b>,</b>
<b>int *</b><i>rowsP</i><b>,</b>
<b>gray *</b><i>maxvalP</i><b> );</b>
<p>
<b>void pgm_writepgminit( </b>
<b>FILE * fp , </b>
<b>int </b><i>cols</i><b>,</b>
<b>int </b><i>rows</i><b>,</b>
<b>gray </b><i>maxval</i><b>,</b>
<b>int </b><i>forceplain</i><b> );</b>
<p>
<b>void pgm_writepgmrow( </b>
<b>FILE *</b><i>fp</i><b>,</b>
<b>gray *</b><i>grayrow</i><b>,</b>
<b>int cols</b><i>,</i>
<b>gray </b><i>maxval</i><b>,</b>
<b>int </b><i>forceplain</i><b> );</b>
<p>
<b>void pgm_writepgm( </b>
<b>FILE *</b><i>fp</i><b>,</b>
<b>gray ** </b><i>grays</i><b>,</b>
<b>int </b><i>cols</i><b>,</b>
<b>int </b><i>rows</i><b>,</b>
<b>gray </b><i>maxval</i><b>,</b>
<b>int </b><i>forceplain</i><b> );</b>
<p>
<b>void pgm_writepgm( </b>
<b>FILE *</b><i>fp</i><b>,</b>
<b>gray **</b><i>grays</i><b>,</b>
<b>int </b><i>cols</i><b>,</b>
<b>int </b><i>rows</i><b>,</b>
<b>gray </b><i>maxval</i><b>,</b>
<b>int </b><i>forceplain</i><b> );</b>
<p>
<b>void pgm_nextimage(</b>
<b>FILE *</b><i>file</i><b>,</b>
<b>int * const </b><i>eofP</i><b>);</b>
<p>
<b>void pgm_check(</b>
<b>FILE * </b><i>file</i><b>,</b>
<b>const enum pm_check_type </b><i>check_type</i><b>,</b>
<b>const int </b><i>format</i><b>,</b>
<b>const int </b><i>cols</i><b>,</b>
<b>const int </b><i>rows</i><b>,</b>
<b>const int </b><i>maxval</i><b>,</b>
<b>enum pm_check_code * const </b><i>retval</i><b>);</b>
<p>
<b>typedef ... gray;</b>
<p>
<b>#define PGM_MAXMAXVAL ...</b>
<p>
<b>#define PGM_OVERALLMAXVAL ...</b>
<p>
<b>#define PGM_FORMAT ...</b>
<p>
<b>#define RPGM_FORMAT ...</b>
<p>
<b>#define PGM_TYPE PGM_FORMAT</b>
<p>
<b>#define </b>
<b>PGM_FORMAT_TYPE(</b><i>format</i><b>)</b>
<b>...</b>
<h2 id="description">DESCRIPTION</h2>
<p>These library functions are part of <a href="index.html">Netpbm</a>.
<h3 id="types">TYPES AND CONSTANTS</h3>
<p>Each <b>gray</b> should contain only the values between <b>0</b>
and <b>PGM_OVERALLMAXVAL</b>.
<p><b>PGM_OVERALLMAXVAL</b> is the maximum value of a maxval in a PGM
file. <b>PGM_MAXMAXVAL</b> 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 <b>PGM_MAXMAXVAL</b> cannot be read or
generated by old PGM processing programs and requires more file space.
<p><b>PGM_FORMAT </b> is the format code for a Plain PGM format image
file. <b>RPGM_FORMAT</b> is the format code for a Raw PGM format
image file. <b>PGM_TYPE </b> is the format type code for the PGM
formats. <b>PGM_FORMAT_TYPE</b> 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.
<h3 id="initialization">INITIALIZATION</h3>
<p><b>pgm_init()</b> is obsolete (at least since Netpbm 9.25 (March 2002)).
Use <a href="libpm.html#initialization"><b>pm_proginit()</b></a> instead.
<p><b>pgm_init()</b> is identical to <b>pm_proginit</b>.
<h3 id="memorymanagement">MEMORY MANAGEMENT</h3>
<b>pgm_allocarray()</b> allocates an array of grays.
<p><b>pgm_allocrow()</b> allocates a row of the given number of grays.
<p><b>pgm_freearray()</b> frees the array allocated with
<b>pgm_allocarray()</b> containing the given number of rows.
<p><b>pgm_freerow()</b> frees a row of grays allocated with
<b>pgm_allocrow()</b>.
<h3 id="reading">READING FILES</h3>
<p>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 <i>format</i> value
returned by <b>pgm_readpgminit()</b> is, however, not translated. It
represents the actual format of the PBM file.
<p><b>pgm_readpgminit()</b> reads the header of a PGM file, returning
all the information from the header and leaving the file positioned
just after the header.
<p><b>pgm_readpgmrow()</b> reads a row of grays into the <i>grayrow
</i> array. <i>format</i>, <i>cols</i>, and <i>maxval </i> are the
values returned by <b>pgm_readpgminit()</b>.
<p><b>pgm_readpgm()</b> reads an entire PGM image into memory,
returning the allocated array as its return value and returning the
information from the header as <i>rows</i>, <i>cols</i>, and
<i>maxval</i>. This function combines <b>pgm_readpgminit()</b>,
<b>pgm_allocarray()</b>, and <b>pgm_readpgmrow()</b>.
<p><b>pgm_readpgminit()</b> and <b>pgm_readpgm</b> 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').
<h3 id="writing">WRITING FILES</h3>
<b>pgm_writepgminit()</b> writes the header for a PGM file and leaves
it positioned just after the header.
<p><i>forceplain</i> is a logical value that tells
<b>pgm_writepgminit() </b> to write a header for a plain PGM format
file, as opposed to a raw PGM format file.
<p><b>pgm_writepgmrow()</b> writes the row <i>grayrow</i> to a PGM
file. For meaningful results, <i>cols</i>, <i>maxval</i>, and
<i>forceplain</i> must be the same as was used with
<b>pgm_writepgminit()</b>.
<p><b>pgm_writepgm()</b> write the header and all data for a PGM
image. This function combines <b>pgm_writepgminit()</b> and
<b>pgm_writepgmrow()</b>.
<h3 id="miscellaneous">MISCELLANEOUS</h3>
<p><b>pgm_nextimage()</b> positions a PGM input file to the next image
in it (so that a subsequent <b>pgm_readpgminit()</b> reads its
header).
<p><b>pgm_nextimage()</b> is analogous to <b>pbm_nextimage()</b>, but
works on PGM and PBM files.
<p><b>pgm_check() </b> checks for the common file integrity error
where the file is the wrong size to contain all the image data.
<p><b>pgm_check() </b> is analogous to <b>pbm_check()</b>, but works
on PGM and PBM files.
<h2 id="seealso">SEE ALSO</h2>
<b><a href="libpbm.html">libpbm</a></b>,
<b><a href="libppm.html">libppm</a></b>,
<b><a href="libpnm.html">libpnm</a></b>
<hr>
<h2 id="index">Table Of Contents</h2>
<ul>
<li><a href="#synopsis">SYNOPSIS</a>
<li><a href="#description">DESCRIPTION</a>
<ul>
<li><a href="#types">TYPES AND CONSTANTS</a>
<li><a href="#initialization">INITIALIZATION</a>
<li><a href="#memorymanagement">MEMORY MANAGEMENT</a>
<li><a href="#reading">READING FILES</a>
<li><a href="#writing">WRITING FILES</a>
<li><a href="#miscellaneous">MISCELLANEOUS</a>
</ul>
<li><a href="#seealso">SEE ALSO</a>
</ul>
</body>
</html>
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