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<?php
/**
* Support for detecting/validating DjVu image files and getting
* some basic file metadata (resolution etc)
*
* File format docs are available in source package for DjVuLibre:
* http://djvulibre.djvuzone.org/
*
*
* Copyright (C) 2006 Brion Vibber <brion@pobox.com>
* http://www.mediawiki.org/
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @package MediaWiki
*/
class DjVuImage {
function __construct( $filename ) {
$this->mFilename = $filename;
}
/**
* Check if the given file is indeed a valid DjVu image file
* @return bool
*/
public function isValid() {
$info = $this->getInfo();
return $info !== false;
}
/**
* Return data in the style of getimagesize()
* @return array or false on failure
*/
public function getImageSize() {
$data = $this->getInfo();
if( $data !== false ) {
$width = $data['width'];
$height = $data['height'];
return array( $width, $height, 'DjVu',
"width=\"$width\" height=\"$height\"" );
}
return false;
}
// ---------
/**
* For debugging; dump the IFF chunk structure
*/
function dump() {
$file = fopen( $this->mFilename, 'rb' );
$header = fread( $file, 12 );
extract( unpack( 'a4magic/a4chunk/NchunkLength', $header ) );
echo "$chunk $chunkLength\n";
$this->dumpForm( $file, $chunkLength, 1 );
fclose( $file );
}
private function dumpForm( $file, $length, $indent ) {
$start = ftell( $file );
$secondary = fread( $file, 4 );
echo str_repeat( ' ', $indent * 4 ) . "($secondary)\n";
while( ftell( $file ) - $start < $length ) {
$chunkHeader = fread( $file, 8 );
if( $chunkHeader == '' ) {
break;
}
extract( unpack( 'a4chunk/NchunkLength', $chunkHeader ) );
echo str_repeat( ' ', $indent * 4 ) . "$chunk $chunkLength\n";
if( $chunk == 'FORM' ) {
$this->dumpForm( $file, $chunkLength, $indent + 1 );
} else {
fseek( $file, $chunkLength, SEEK_CUR );
if( $chunkLength & 1 == 1 ) {
// Padding byte between chunks
fseek( $file, 1, SEEK_CUR );
}
}
}
}
function getInfo() {
$file = fopen( $this->mFilename, 'rb' );
if( $file === false ) {
wfDebug( __METHOD__ . ": missing or failed file read\n" );
return false;
}
$header = fread( $file, 16 );
$info = false;
if( strlen( $header ) < 16 ) {
wfDebug( __METHOD__ . ": too short file header\n" );
} else {
extract( unpack( 'a4magic/a4form/NformLength/a4subtype', $header ) );
if( $magic != 'AT&T' ) {
wfDebug( __METHOD__ . ": not a DjVu file\n" );
} elseif( $subtype == 'DJVU' ) {
// Single-page document
$info = $this->getPageInfo( $file, $formLength );
} elseif( $subtype == 'DJVM' ) {
// Multi-page document
$info = $this->getMultiPageInfo( $file, $formLength );
} else {
wfDebug( __METHOD__ . ": unrecognized DJVU file type '$formType'\n" );
}
}
fclose( $file );
return $info;
}
private function readChunk( $file ) {
$header = fread( $file, 8 );
if( strlen( $header ) < 8 ) {
return array( false, 0 );
} else {
extract( unpack( 'a4chunk/Nlength', $header ) );
return array( $chunk, $length );
}
}
private function skipChunk( $file, $chunkLength ) {
fseek( $file, $chunkLength, SEEK_CUR );
if( $chunkLength & 0x01 == 1 && !feof( $file ) ) {
// padding byte
fseek( $file, 1, SEEK_CUR );
}
}
private function getMultiPageInfo( $file, $formLength ) {
// For now, we'll just look for the first page in the file
// and report its information, hoping others are the same size.
$start = ftell( $file );
do {
list( $chunk, $length ) = $this->readChunk( $file );
if( !$chunk ) {
break;
}
if( $chunk == 'FORM' ) {
$subtype = fread( $file, 4 );
if( $subtype == 'DJVU' ) {
wfDebug( __METHOD__ . ": found first subpage\n" );
return $this->getPageInfo( $file, $length );
}
$this->skipChunk( $file, $length - 4 );
} else {
wfDebug( __METHOD__ . ": skipping '$chunk' chunk\n" );
$this->skipChunk( $file, $length );
}
} while( $length != 0 && !feof( $file ) && ftell( $file ) - $start < $formLength );
wfDebug( __METHOD__ . ": multi-page DJVU file contained no pages\n" );
return false;
}
private function getPageInfo( $file, $formLength ) {
list( $chunk, $length ) = $this->readChunk( $file );
if( $chunk != 'INFO' ) {
wfDebug( __METHOD__ . ": expected INFO chunk, got '$chunk'\n" );
return false;
}
if( $length < 9 ) {
wfDebug( __METHOD__ . ": INFO should be 9 or 10 bytes, found $length\n" );
return false;
}
$data = fread( $file, $length );
if( strlen( $data ) < $length ) {
wfDebug( __METHOD__ . ": INFO chunk cut off\n" );
return false;
}
extract( unpack(
'nwidth/' .
'nheight/' .
'Cminor/' .
'Cmajor/' .
'vresolution/' .
'Cgamma', $data ) );
# Newer files have rotation info in byte 10, but we don't use it yet.
return array(
'width' => $width,
'height' => $height,
'version' => "$major.$minor",
'resolution' => $resolution,
'gamma' => $gamma / 10.0 );
}
/**
* Return an XML string describing the DjVu image
* @return string
*/
function retrieveMetaData() {
global $wgDjvuToXML;
if ( isset( $wgDjvuToXML ) ) {
$cmd = $wgDjvuToXML . ' --without-anno --without-text ' . $this->mFilename;
$xml = wfShellExec( $cmd, $retval );
} else {
$xml = null;
}
return $xml;
}
}
?>
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