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
  39         private $reader = null;
  40         private $mDebug = false;
  41         private $metadata = Array();
  42
  43         /**
  44          * Constructor
  45          *
  46          * Creates an SVGReader drawing from the source provided
  47          * @param $source String: URI from which to read
  48          */
  49         function __construct( $source ) {
  50                 $this->reader = new XMLReader();
  51                 $this->reader->open( $source, null, LIBXML_NOERROR | LIBXML_NOWARNING );
  52
  53                 $this->metadata['width'] = self::DEFAULT_WIDTH;
  54                 $this->metadata['height'] = self::DEFAULT_HEIGHT;
  55
  56                 $this->read();
  57         }
  58
  59         /*
  60          * @return Array with the known metadata
  61          */
  62         public function getMetadata() {
  63                 return $this->metadata;
  64         }
  65
  66         /*
  67          * Read the SVG
  68          */
  69         public function read() {
  70                 $keepReading = $this->reader->read();
  71
  72                 /* Skip until first element */
  73                 while( $keepReading && $this->reader->nodeType != XmlReader::ELEMENT ) {
  74                         $keepReading = $this->reader->read();
  75                 }
  76
  77                 if ( !$this->qualifiedNameEquals( $this->reader->name, 'svg', 'svg' ) ) {
  78                         throw new MWException( "Expected <svg> tag, got ".
  79                                 $this->reader->name );
  80                 }
  81                 $this->debug( "<svg> tag is correct." );
  82                 $this->handleSVGAttribs();
  83
  84                 $exitDepth =  $this->reader->depth;
  85                 $keepReading = $this->reader->read();
  86                 $skip = false;
  87                 while ( $keepReading ) {
  88                         $tag = $this->reader->name;
  89                         $type = $this->reader->nodeType;
  90
  91                         $this->debug( "$tag" );
  92
  93                         if ( $this->qualifiedNameEquals( $tag, 'svg', 'svg' ) && $type == XmlReader::END_ELEMENT && $this->reader->depth <= $exitDepth ) {
  94                                 break;
  95                         } elseif ( $this->qualifiedNameEquals( $tag, 'svg', 'title' ) ) {
  96                                 $this->readField( $tag, 'title' );
  97                         } elseif ( $this->qualifiedNameEquals( $tag, 'svg', 'desc' )  ) {
  98                                 $this->readField( $tag, 'description' );
  99                         } elseif ( $this->qualifiedNameEquals( $tag, 'svg', 'metadata' ) && $type == XmlReader::ELEMENT ) {
 100                                 $this->readXml( $tag, 'metadata' );
 101                         } elseif ( $tag !== '#text' ) {
 102                                 $this->debug( "Unhandled top-level XML tag $tag" );
 103                                 $this->animateFilter( $tag );
 104                                 //$skip = true;
 105                         }
 106
 107                         if ($skip) {
 108                                 $keepReading = $this->reader->next();
 109                                 $skip = false;
 110                                 $this->debug( "Skip" );
 111                         } else {
 112                                 $keepReading = $this->reader->read();
 113                         }
 114                 }
 115
 116                 return true;
 117         }
 118
 119         /*
 120          * Read a textelement from an element
 121          *
 122          * @param String $name of the element that we are reading from
 123          * @param String $metafield that we will fill with the result
 124          */
 125         private function readField( $name, $metafield=null ) {
 126                 $this->debug ( "Read field $metafield" );
 127                 if( !$metafield || $this->reader->nodeType != XmlReader::ELEMENT ) {
 128                         return;
 129                 }
 130                 $keepReading = $this->reader->read();
 131                 while( $keepReading ) {
 132                         if( $this->reader->name == $name && $this->reader->nodeType == XmlReader::END_ELEMENT ) {
 133                                 break;
 134                         } elseif( $this->reader->nodeType == XmlReader::TEXT ){
 135                                 $this->metadata[$metafield] = $this->reader->value;
 136                         }
 137                         $keepReading = $this->reader->read();
 138                 }
 139         }
 140
 141         /*
 142          * Read an XML snippet from an element
 143          *
 144          * @param String $metafield that we will fill with the result
 145          */
 146         private function readXml( $metafield=null ) {
 147                 $this->debug ( "Read top level metadata" );
 148                 if( !$metafield || $this->reader->nodeType != XmlReader::ELEMENT ) {
 149                         return;
 150                 }
 151                 // TODO: find and store type of xml snippet. metadata['metadataType'] = "rdf"
 152                 $this->metadata[$metafield] = $this->reader->readInnerXML();
 153                 $this->reader->next();
 154         }
 155
 156         /*
 157          * Filter all children, looking for animate elements
 158          *
 159          * @param String $name of the element that we are reading from
 160          */
 161         private function animateFilter( $name ) {
 162                 $this->debug ( "animate filter" );
 163                 if( $this->reader->nodeType != XmlReader::ELEMENT ) {
 164                         return;
 165                 }
 166                 $exitDepth =  $this->reader->depth;
 167                 $keepReading = $this->reader->read();
 168                 while( $keepReading ) {
 169                         if( $this->reader->name == $name && $this->reader->depth <= $exitDepth
 170                                 && $this->reader->nodeType == XmlReader::END_ELEMENT ) {
 171                                 break;
 172                         } elseif ( $this->reader->nodeType == XmlReader::ELEMENT ) {
 173                                 switch( $this->reader->name ) {
 174                                         case 'animate':
 175                                         case 'svg:animate':
 176                                         case 'set':
 177                                         case 'svg:set':
 178                                         case 'animateMotion':
 179                                         case 'svg:animateMotion':
 180                                         case 'animateColor':
 181                                         case 'svg:animateColor':
 182                                         case 'animateTransform':
 183                                         case 'svg:animateTransform':
 184                                                 $this->debug( "HOUSTON WE HAVE ANIMATION" );
 185                                                 $this->metadata['animated'] = true;
 186                                                 break;
 187                                 }
 188                         }
 189                         $keepReading = $this->reader->read();
 190                 }
 191         }
 192
 193         private function throwXmlError( $err ) {
 194                 $this->debug( "FAILURE: $err" );
 195                 wfDebug( "SVGReader XML error: $err\n" );
 196         }
 197
 198         private function debug( $data ) {
 199                 if( $this->mDebug ) {
 200                         wfDebug( "SVGReader: $data\n" );
 201                 }
 202         }
 203
 204         private function warn( $data ) {
 205                 wfDebug( "SVGReader: $data\n" );
 206         }
 207
 208         private function notice( $data ) {
 209                 wfDebug( "SVGReader WARN: $data\n" );
 210         }
 211
 212         /*
 213          * Parse the attributes of an SVG element
 214          *
 215          * The parser has to be in the start element of <svg>
 216          */
 217         private function handleSVGAttribs( ) {
 218                 $defaultWidth = self::DEFAULT_WIDTH;
 219                 $defaultHeight = self::DEFAULT_HEIGHT;
 220                 $aspect = 1.0;
 221                 $width = null;
 222                 $height = null;
 223
 224                 if( $this->reader->getAttribute('viewBox') ) {
 225                         // min-x min-y width height
 226                         $viewBox = preg_split( '/\s+/', trim( $this->reader->getAttribute('viewBox') ) );
 227                         if( count( $viewBox ) == 4 ) {
 228                                 $viewWidth = $this->scaleSVGUnit( $viewBox[2] );
 229                                 $viewHeight = $this->scaleSVGUnit( $viewBox[3] );
 230                                 if( $viewWidth > 0 && $viewHeight > 0 ) {
 231                                         $aspect = $viewWidth / $viewHeight;
 232                                         $defaultHeight = $defaultWidth / $aspect;
 233                                 }
 234                         }
 235                 }
 236                 if( $this->reader->getAttribute('width') ) {
 237                         $width = $this->scaleSVGUnit( $this->reader->getAttribute('width'), $defaultWidth );
 238                 }
 239                 if( $this->reader->getAttribute('height') ) {
 240                         $height = $this->scaleSVGUnit( $this->reader->getAttribute('height'), $defaultHeight );
 241                 }
 242
 243                 if( !isset( $width ) && !isset( $height ) ) {
 244                         $width = $defaultWidth;
 245                         $height = $width / $aspect;
 246                 } elseif( isset( $width ) && !isset( $height ) ) {
 247                         $height = $width / $aspect;
 248                 } elseif( isset( $height ) && !isset( $width ) ) {
 249                         $width = $height * $aspect;
 250                 }
 251
 252                 if( $width > 0 && $height > 0 ) {
 253                         $this->metadata['width'] = intval( round( $width ) );
 254                         $this->metadata['height'] = intval( round( $height ) );
 255                 }
 256         }
 257
 258         /**
 259          * Return a rounded pixel equivalent for a labeled CSS/SVG length.
 260          * http://www.w3.org/TR/SVG11/coords.html#UnitIdentifiers
 261          *
 262          * @param $length String: CSS/SVG length.
 263          * @param $viewportSize: Float optional scale for percentage units...
 264          * @return float: length in pixels
 265          */
 266         static function scaleSVGUnit( $length, $viewportSize=512 ) {
 267                 static $unitLength = array(
 268                         'px' => 1.0,
 269                         'pt' => 1.25,
 270                         'pc' => 15.0,
 271                         'mm' => 3.543307,
 272                         'cm' => 35.43307,
 273                         'in' => 90.0,
 274                         'em' => 16.0, // fake it?
 275                         'ex' => 12.0, // fake it?
 276                         ''   => 1.0, // "User units" pixels by default
 277                         );
 278                 $matches = array();
 279                 if( preg_match( '/^\s*(\d+(?:\.\d+)?)(em|ex|px|pt|pc|cm|mm|in|%|)\s*$/', $length, $matches ) ) {
 280                         $length = floatval( $matches[1] );
 281                         $unit = $matches[2];
 282                         if( $unit == '%' ) {
 283                                 return $length * 0.01 * $viewportSize;
 284                         } else {
 285                                 return $length * $unitLength[$unit];
 286                         }
 287                 } else {
 288                         // Assume pixels
 289                         return floatval( $length );
 290                 }
 291         }
 292
 293         /**
 294          * XML namespace check
 295          *
 296          * Check if a read node name matches the expected nodeName
 297          * @param $qualifiedName as read by XMLReader
 298          * @param $prefix the namespace prefix that you expect for this element, defaults to svg namespace
 299          * @param $localName the localName part of the element that you want to match
 300          *
 301          * @return boolean
 302          */
 303         private function qualifiedNameEquals( $qualifiedName, $prefix="svg", $localName ) {
 304                 if( ($qualifiedName == $localName && $prefix == "svg" ) ||
 305                      $qualifiedName == ($prefix . ":" . $localName) ) {
 306                         return true;
 307                 }
 308                 return false;
 309         }
 310 }