includes/media/SVGMetadataExtractor.php

   1 <?php
   2 /**
   3  * SVGMetadataExtractor.php
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Media
  22  * @author Derk-Jan Hartman <hartman _at_ videolan d0t org>
  23  * @author Brion Vibber
  24  * @copyright Copyright © 2010-2010 Brion Vibber, Derk-Jan Hartman
  25  * @license http://www.gnu.org/copyleft/gpl.html GNU General Public License
  26  */
  27
  28 class SVGMetadataExtractor {
  29         static function getMetadata( $filename ) {
  30                 $svg = new SVGReader( $filename );
  31                 return $svg->getMetadata();
  32         }
  33 }
  34
  35 class SVGReader {
  36         const DEFAULT_WIDTH = 512;
  37         const DEFAULT_HEIGHT = 512;
  38         const NS_SVG = 'http://www.w3.org/2000/svg';
  39
  40         private $reader = null;
  41         private $mDebug = false;
  42         private $metadata = Array();
  43
  44         /**
  45          * Constructor
  46          *
  47          * Creates an SVGReader drawing from the source provided
  48          * @param $source String: URI from which to read
  49          */
  50         function __construct( $source ) {
  51                 global $wgSVGMetadataCutoff;
  52                 $this->reader = new XMLReader();
  53
  54                 // Don't use $file->getSize() since file object passed to SVGHandler::getMetadata is bogus.
  55                 $size = filesize( $source );
  56                 if ( $size === false ) {
  57                         throw new MWException( "Error getting filesize of SVG." );
  58                 }
  59
  60                 if ( $size > $wgSVGMetadataCutoff ) {
  61                         $this->debug( "SVG is $size bytes, which is bigger than $wgSVGMetadataCutoff. Truncating." );
  62                         $contents = file_get_contents( $source, false, null, -1, $wgSVGMetadataCutoff );
  63                         if ($contents === false) {
  64                                 throw new MWException( 'Error reading SVG file.' );
  65                         }
  66                         $this->reader->XML( $contents, null, LIBXML_NOERROR | LIBXML_NOWARNING );
  67                 } else {
  68                         $this->reader->open( $source, null, LIBXML_NOERROR | LIBXML_NOWARNING );
  69                 }
  70
  71                 $this->metadata['width'] = self::DEFAULT_WIDTH;
  72                 $this->metadata['height'] = self::DEFAULT_HEIGHT;
  73
  74                 // Because we cut off the end of the svg making an invalid one. Complicated
  75                 // try catch thing to make sure warnings get restored. Seems like there should
  76                 // be a better way.
  77                 wfSuppressWarnings();
  78                 try {
  79                         $this->read();
  80                 } catch( Exception $e ) {
  81                         wfRestoreWarnings();
  82                         throw $e;
  83                 }
  84                 wfRestoreWarnings();
  85         }
  86
  87         /*
  88          * @return Array with the known metadata
  89          */
  90         public function getMetadata() {
  91                 return $this->metadata;
  92         }
  93
  94         /*
  95          * Read the SVG
  96          */
  97         public function read() {
  98                 $keepReading = $this->reader->read();
  99
 100                 /* Skip until first element */
 101                 while( $keepReading && $this->reader->nodeType != XmlReader::ELEMENT ) {
 102                         $keepReading = $this->reader->read();
 103                 }
 104
 105                 if ( $this->reader->localName != 'svg' || $this->reader->namespaceURI != self::NS_SVG ) {
 106                         throw new MWException( "Expected <svg> tag, got ".
 107                                 $this->reader->localName . " in NS " . $this->reader->namespaceURI );
 108                 }
 109                 $this->debug( "<svg> tag is correct." );
 110                 $this->handleSVGAttribs();
 111
 112                 $exitDepth =  $this->reader->depth;
 113                 $keepReading = $this->reader->read();
 114                 while ( $keepReading ) {
 115                         $tag = $this->reader->localName;
 116                         $type = $this->reader->nodeType;
 117                         $isSVG = ($this->reader->namespaceURI == self::NS_SVG);
 118
 119                         $this->debug( "$tag" );
 120
 121                         if ( $isSVG && $tag == 'svg' && $type == XmlReader::END_ELEMENT && $this->reader->depth <= $exitDepth ) {
 122                                 break;
 123                         } elseif ( $isSVG && $tag == 'title' ) {
 124                                 $this->readField( $tag, 'title' );
 125                         } elseif ( $isSVG && $tag == 'desc' ) {
 126                                 $this->readField( $tag, 'description' );
 127                         } elseif ( $isSVG && $tag == 'metadata' && $type == XmlReader::ELEMENT ) {
 128                                 $this->readXml( $tag, 'metadata' );
 129                         } elseif ( $tag !== '#text' ) {
 130                                 $this->debug( "Unhandled top-level XML tag $tag" );
 131
 132                                 if ( !isset( $this->metadata['animated'] ) ) {
 133                                         // Recurse into children of current tag, looking for animation.
 134                                         $this->animateFilter( $tag );
 135                                 }
 136                         }
 137
 138                         // Goto next element, which is sibling of current (Skip children).
 139                         $keepReading = $this->reader->next();
 140                 }
 141
 142                 return true;
 143         }
 144
 145         /*
 146          * Read a textelement from an element
 147          *
 148          * @param String $name of the element that we are reading from
 149          * @param String $metafield that we will fill with the result
 150          */
 151         private function readField( $name, $metafield=null ) {
 152                 $this->debug ( "Read field $metafield" );
 153                 if( !$metafield || $this->reader->nodeType != XmlReader::ELEMENT ) {
 154                         return;
 155                 }
 156                 $keepReading = $this->reader->read();
 157                 while( $keepReading ) {
 158                         if( $this->reader->localName == $name && $this->namespaceURI == self::NS_SVG && $this->reader->nodeType == XmlReader::END_ELEMENT ) {
 159                                 break;
 160                         } elseif( $this->reader->nodeType == XmlReader::TEXT ){
 161                                 $this->metadata[$metafield] = trim( $this->reader->value );
 162                         }
 163                         $keepReading = $this->reader->read();
 164                 }
 165         }
 166
 167         /*
 168          * Read an XML snippet from an element
 169          *
 170          * @param String $metafield that we will fill with the result
 171          */
 172         private function readXml( $metafield=null ) {
 173                 $this->debug ( "Read top level metadata" );
 174                 if( !$metafield || $this->reader->nodeType != XmlReader::ELEMENT ) {
 175                         return;
 176                 }
 177                 // TODO: find and store type of xml snippet. metadata['metadataType'] = "rdf"
 178                 $this->metadata[$metafield] = trim( $this->reader->readInnerXML() );
 179                 $this->reader->next();
 180         }
 181
 182         /*
 183          * Filter all children, looking for animate elements
 184          *
 185          * @param String $name of the element that we are reading from
 186          */
 187         private function animateFilter( $name ) {
 188                 $this->debug ( "animate filter" );
 189                 if( $this->reader->nodeType != XmlReader::ELEMENT ) {
 190                         return;
 191                 }
 192                 $exitDepth =  $this->reader->depth;
 193                 $keepReading = $this->reader->read();
 194                 while( $keepReading ) {
 195                         if( $this->reader->localName == $name && $this->reader->depth <= $exitDepth
 196                                 && $this->reader->nodeType == XmlReader::END_ELEMENT ) {
 197                                 break;
 198                         } elseif ( $this->reader->namespaceURI == self::NS_SVG && $this->reader->nodeType == XmlReader::ELEMENT ) {
 199                                 switch( $this->reader->localName ) {
 200                                         case 'animate':
 201                                         case 'set':
 202                                         case 'animateMotion':
 203                                         case 'animateColor':
 204                                         case 'animateTransform':
 205                                                 $this->debug( "HOUSTON WE HAVE ANIMATION" );
 206                                                 $this->metadata['animated'] = true;
 207                                                 break;
 208                                 }
 209                         }
 210                         $keepReading = $this->reader->read();
 211                 }
 212         }
 213
 214         private function throwXmlError( $err ) {
 215                 $this->debug( "FAILURE: $err" );
 216                 wfDebug( "SVGReader XML error: $err\n" );
 217         }
 218
 219         private function debug( $data ) {
 220                 if( $this->mDebug ) {
 221                         wfDebug( "SVGReader: $data\n" );
 222                 }
 223         }
 224
 225         private function warn( $data ) {
 226                 wfDebug( "SVGReader: $data\n" );
 227         }
 228
 229         private function notice( $data ) {
 230                 wfDebug( "SVGReader WARN: $data\n" );
 231         }
 232
 233         /*
 234          * Parse the attributes of an SVG element
 235          *
 236          * The parser has to be in the start element of <svg>
 237          */
 238         private function handleSVGAttribs( ) {
 239                 $defaultWidth = self::DEFAULT_WIDTH;
 240                 $defaultHeight = self::DEFAULT_HEIGHT;
 241                 $aspect = 1.0;
 242                 $width = null;
 243                 $height = null;
 244
 245                 if( $this->reader->getAttribute('viewBox') ) {
 246                         // min-x min-y width height
 247                         $viewBox = preg_split( '/\s+/', trim( $this->reader->getAttribute('viewBox') ) );
 248                         if( count( $viewBox ) == 4 ) {
 249                                 $viewWidth = $this->scaleSVGUnit( $viewBox[2] );
 250                                 $viewHeight = $this->scaleSVGUnit( $viewBox[3] );
 251                                 if( $viewWidth > 0 && $viewHeight > 0 ) {
 252                                         $aspect = $viewWidth / $viewHeight;
 253                                         $defaultHeight = $defaultWidth / $aspect;
 254                                 }
 255                         }
 256                 }
 257                 if( $this->reader->getAttribute('width') ) {
 258                         $width = $this->scaleSVGUnit( $this->reader->getAttribute('width'), $defaultWidth );
 259                 }
 260                 if( $this->reader->getAttribute('height') ) {
 261                         $height = $this->scaleSVGUnit( $this->reader->getAttribute('height'), $defaultHeight );
 262                 }
 263
 264                 if( !isset( $width ) && !isset( $height ) ) {
 265                         $width = $defaultWidth;
 266                         $height = $width / $aspect;
 267                 } elseif( isset( $width ) && !isset( $height ) ) {
 268                         $height = $width / $aspect;
 269                 } elseif( isset( $height ) && !isset( $width ) ) {
 270                         $width = $height * $aspect;
 271                 }
 272
 273                 if( $width > 0 && $height > 0 ) {
 274                         $this->metadata['width'] = intval( round( $width ) );
 275                         $this->metadata['height'] = intval( round( $height ) );
 276                 }
 277         }
 278
 279         /**
 280          * Return a rounded pixel equivalent for a labeled CSS/SVG length.
 281          * http://www.w3.org/TR/SVG11/coords.html#UnitIdentifiers
 282          *
 283          * @param $length String: CSS/SVG length.
 284          * @param $viewportSize: Float optional scale for percentage units...
 285          * @return float: length in pixels
 286          */
 287         static function scaleSVGUnit( $length, $viewportSize=512 ) {
 288                 static $unitLength = array(
 289                         'px' => 1.0,
 290                         'pt' => 1.25,
 291                         'pc' => 15.0,
 292                         'mm' => 3.543307,
 293                         'cm' => 35.43307,
 294                         'in' => 90.0,
 295                         'em' => 16.0, // fake it?
 296                         'ex' => 12.0, // fake it?
 297                         ''   => 1.0, // "User units" pixels by default
 298                         );
 299                 $matches = array();
 300                 if( preg_match( '/^\s*(\d+(?:\.\d+)?)(em|ex|px|pt|pc|cm|mm|in|%|)\s*$/', $length, $matches ) ) {
 301                         $length = floatval( $matches[1] );
 302                         $unit = $matches[2];
 303                         if( $unit == '%' ) {
 304                                 return $length * 0.01 * $viewportSize;
 305                         } else {
 306                                 return $length * $unitLength[$unit];
 307                         }
 308                 } else {
 309                         // Assume pixels
 310                         return floatval( $length );
 311                 }
 312         }
 313 }