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[mediawiki.git] / includes / media / SVGMetadataExtractor.php
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1 <?php
2 /**
3 * Extraction of SVG image metadata.
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.
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.
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
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
28 /**
29 * @ingroup Media
31 class SVGMetadataExtractor {
32 static function getMetadata( $filename ) {
33 $svg = new SVGReader( $filename );
35 return $svg->getMetadata();
39 /**
40 * @ingroup Media
42 class SVGReader {
43 const DEFAULT_WIDTH = 512;
44 const DEFAULT_HEIGHT = 512;
45 const NS_SVG = 'http://www.w3.org/2000/svg';
46 const LANG_PREFIX_MATCH = 1;
47 const LANG_FULL_MATCH = 2;
49 /** @var null|XMLReader */
50 private $reader = null;
52 /** @var bool */
53 private $mDebug = false;
55 /** @var array */
56 private $metadata = [];
57 private $languages = [];
58 private $languagePrefixes = [];
60 /**
61 * Constructor
63 * Creates an SVGReader drawing from the source provided
64 * @param string $source URI from which to read
65 * @throws MWException|Exception
67 function __construct( $source ) {
68 global $wgSVGMetadataCutoff;
69 $this->reader = new XMLReader();
71 // Don't use $file->getSize() since file object passed to SVGHandler::getMetadata is bogus.
72 $size = filesize( $source );
73 if ( $size === false ) {
74 throw new MWException( "Error getting filesize of SVG." );
77 if ( $size > $wgSVGMetadataCutoff ) {
78 $this->debug( "SVG is $size bytes, which is bigger than $wgSVGMetadataCutoff. Truncating." );
79 $contents = file_get_contents( $source, false, null, -1, $wgSVGMetadataCutoff );
80 if ( $contents === false ) {
81 throw new MWException( 'Error reading SVG file.' );
83 $this->reader->XML( $contents, null, LIBXML_NOERROR | LIBXML_NOWARNING );
84 } else {
85 $this->reader->open( $source, null, LIBXML_NOERROR | LIBXML_NOWARNING );
88 // Expand entities, since Adobe Illustrator uses them for xmlns
89 // attributes (bug 31719). Note that libxml2 has some protection
90 // against large recursive entity expansions so this is not as
91 // insecure as it might appear to be. However, it is still extremely
92 // insecure. It's necessary to wrap any read() calls with
93 // libxml_disable_entity_loader() to avoid arbitrary local file
94 // inclusion, or even arbitrary code execution if the expect
95 // extension is installed (bug 46859).
96 $oldDisable = libxml_disable_entity_loader( true );
97 $this->reader->setParserProperty( XMLReader::SUBST_ENTITIES, true );
99 $this->metadata['width'] = self::DEFAULT_WIDTH;
100 $this->metadata['height'] = self::DEFAULT_HEIGHT;
102 // The size in the units specified by the SVG file
103 // (for the metadata box)
104 // Per the SVG spec, if unspecified, default to '100%'
105 $this->metadata['originalWidth'] = '100%';
106 $this->metadata['originalHeight'] = '100%';
108 // Because we cut off the end of the svg making an invalid one. Complicated
109 // try catch thing to make sure warnings get restored. Seems like there should
110 // be a better way.
111 MediaWiki\suppressWarnings();
112 try {
113 $this->read();
114 } catch ( Exception $e ) {
115 // Note, if this happens, the width/height will be taken to be 0x0.
116 // Should we consider it the default 512x512 instead?
117 MediaWiki\restoreWarnings();
118 libxml_disable_entity_loader( $oldDisable );
119 throw $e;
121 MediaWiki\restoreWarnings();
122 libxml_disable_entity_loader( $oldDisable );
126 * @return array Array with the known metadata
128 public function getMetadata() {
129 return $this->metadata;
133 * Read the SVG
134 * @throws MWException
135 * @return bool
137 protected function read() {
138 $keepReading = $this->reader->read();
140 /* Skip until first element */
141 while ( $keepReading && $this->reader->nodeType != XMLReader::ELEMENT ) {
142 $keepReading = $this->reader->read();
145 if ( $this->reader->localName != 'svg' || $this->reader->namespaceURI != self::NS_SVG ) {
146 throw new MWException( "Expected <svg> tag, got " .
147 $this->reader->localName . " in NS " . $this->reader->namespaceURI );
149 $this->debug( "<svg> tag is correct." );
150 $this->handleSVGAttribs();
152 $exitDepth = $this->reader->depth;
153 $keepReading = $this->reader->read();
154 while ( $keepReading ) {
155 $tag = $this->reader->localName;
156 $type = $this->reader->nodeType;
157 $isSVG = ( $this->reader->namespaceURI == self::NS_SVG );
159 $this->debug( "$tag" );
161 if ( $isSVG && $tag == 'svg' && $type == XMLReader::END_ELEMENT
162 && $this->reader->depth <= $exitDepth
164 break;
165 } elseif ( $isSVG && $tag == 'title' ) {
166 $this->readField( $tag, 'title' );
167 } elseif ( $isSVG && $tag == 'desc' ) {
168 $this->readField( $tag, 'description' );
169 } elseif ( $isSVG && $tag == 'metadata' && $type == XMLReader::ELEMENT ) {
170 $this->readXml( $tag, 'metadata' );
171 } elseif ( $isSVG && $tag == 'script' ) {
172 // We normally do not allow scripted svgs.
173 // However its possible to configure MW to let them
174 // in, and such files should be considered animated.
175 $this->metadata['animated'] = true;
176 } elseif ( $tag !== '#text' ) {
177 $this->debug( "Unhandled top-level XML tag $tag" );
179 // Recurse into children of current tag, looking for animation and languages.
180 $this->animateFilterAndLang( $tag );
183 // Goto next element, which is sibling of current (Skip children).
184 $keepReading = $this->reader->next();
187 $this->reader->close();
189 $this->metadata['translations'] = $this->languages + $this->languagePrefixes;
191 return true;
195 * Read a textelement from an element
197 * @param string $name Name of the element that we are reading from
198 * @param string $metafield Field that we will fill with the result
200 private function readField( $name, $metafield = null ) {
201 $this->debug( "Read field $metafield" );
202 if ( !$metafield || $this->reader->nodeType != XMLReader::ELEMENT ) {
203 return;
205 $keepReading = $this->reader->read();
206 while ( $keepReading ) {
207 if ( $this->reader->localName == $name
208 && $this->reader->namespaceURI == self::NS_SVG
209 && $this->reader->nodeType == XMLReader::END_ELEMENT
211 break;
212 } elseif ( $this->reader->nodeType == XMLReader::TEXT ) {
213 $this->metadata[$metafield] = trim( $this->reader->value );
215 $keepReading = $this->reader->read();
220 * Read an XML snippet from an element
222 * @param string $metafield Field that we will fill with the result
223 * @throws MWException
225 private function readXml( $metafield = null ) {
226 $this->debug( "Read top level metadata" );
227 if ( !$metafield || $this->reader->nodeType != XMLReader::ELEMENT ) {
228 return;
230 // @todo Find and store type of xml snippet. metadata['metadataType'] = "rdf"
231 if ( method_exists( $this->reader, 'readInnerXML' ) ) {
232 $this->metadata[$metafield] = trim( $this->reader->readInnerXml() );
233 } else {
234 throw new MWException( "The PHP XMLReader extension does not come " .
235 "with readInnerXML() method. Your libxml is probably out of " .
236 "date (need 2.6.20 or later)." );
238 $this->reader->next();
242 * Filter all children, looking for animated elements.
243 * Also get a list of languages that can be targeted.
245 * @param string $name Name of the element that we are reading from
247 private function animateFilterAndLang( $name ) {
248 $this->debug( "animate filter for tag $name" );
249 if ( $this->reader->nodeType != XMLReader::ELEMENT ) {
250 return;
252 if ( $this->reader->isEmptyElement ) {
253 return;
255 $exitDepth = $this->reader->depth;
256 $keepReading = $this->reader->read();
257 while ( $keepReading ) {
258 if ( $this->reader->localName == $name && $this->reader->depth <= $exitDepth
259 && $this->reader->nodeType == XMLReader::END_ELEMENT
261 break;
262 } elseif ( $this->reader->namespaceURI == self::NS_SVG
263 && $this->reader->nodeType == XMLReader::ELEMENT
265 $sysLang = $this->reader->getAttribute( 'systemLanguage' );
266 if ( !is_null( $sysLang ) && $sysLang !== '' ) {
267 // See http://www.w3.org/TR/SVG/struct.html#SystemLanguageAttribute
268 $langList = explode( ',', $sysLang );
269 foreach ( $langList as $langItem ) {
270 $langItem = trim( $langItem );
271 if ( Language::isWellFormedLanguageTag( $langItem ) ) {
272 $this->languages[$langItem] = self::LANG_FULL_MATCH;
274 // Note, the standard says that any prefix should work,
275 // here we do only the initial prefix, since that will catch
276 // 99% of cases, and we are going to compare against fallbacks.
277 // This differs mildly from how the spec says languages should be
278 // handled, however it matches better how the MediaWiki language
279 // preference is generally handled.
280 $dash = strpos( $langItem, '-' );
281 // Intentionally checking both !false and > 0 at the same time.
282 if ( $dash ) {
283 $itemPrefix = substr( $langItem, 0, $dash );
284 if ( Language::isWellFormedLanguageTag( $itemPrefix ) ) {
285 $this->languagePrefixes[$itemPrefix] = self::LANG_PREFIX_MATCH;
290 switch ( $this->reader->localName ) {
291 case 'script':
292 // Normally we disallow files with
293 // <script>, but its possible
294 // to configure MW to disable
295 // such checks.
296 case 'animate':
297 case 'set':
298 case 'animateMotion':
299 case 'animateColor':
300 case 'animateTransform':
301 $this->debug( "HOUSTON WE HAVE ANIMATION" );
302 $this->metadata['animated'] = true;
303 break;
306 $keepReading = $this->reader->read();
310 // @todo FIXME: Unused, remove?
311 private function throwXmlError( $err ) {
312 $this->debug( "FAILURE: $err" );
313 wfDebug( "SVGReader XML error: $err\n" );
316 private function debug( $data ) {
317 if ( $this->mDebug ) {
318 wfDebug( "SVGReader: $data\n" );
323 * Parse the attributes of an SVG element
325 * The parser has to be in the start element of "<svg>"
327 private function handleSVGAttribs() {
328 $defaultWidth = self::DEFAULT_WIDTH;
329 $defaultHeight = self::DEFAULT_HEIGHT;
330 $aspect = 1.0;
331 $width = null;
332 $height = null;
334 if ( $this->reader->getAttribute( 'viewBox' ) ) {
335 // min-x min-y width height
336 $viewBox = preg_split( '/\s+/', trim( $this->reader->getAttribute( 'viewBox' ) ) );
337 if ( count( $viewBox ) == 4 ) {
338 $viewWidth = $this->scaleSVGUnit( $viewBox[2] );
339 $viewHeight = $this->scaleSVGUnit( $viewBox[3] );
340 if ( $viewWidth > 0 && $viewHeight > 0 ) {
341 $aspect = $viewWidth / $viewHeight;
342 $defaultHeight = $defaultWidth / $aspect;
346 if ( $this->reader->getAttribute( 'width' ) ) {
347 $width = $this->scaleSVGUnit( $this->reader->getAttribute( 'width' ), $defaultWidth );
348 $this->metadata['originalWidth'] = $this->reader->getAttribute( 'width' );
350 if ( $this->reader->getAttribute( 'height' ) ) {
351 $height = $this->scaleSVGUnit( $this->reader->getAttribute( 'height' ), $defaultHeight );
352 $this->metadata['originalHeight'] = $this->reader->getAttribute( 'height' );
355 if ( !isset( $width ) && !isset( $height ) ) {
356 $width = $defaultWidth;
357 $height = $width / $aspect;
358 } elseif ( isset( $width ) && !isset( $height ) ) {
359 $height = $width / $aspect;
360 } elseif ( isset( $height ) && !isset( $width ) ) {
361 $width = $height * $aspect;
364 if ( $width > 0 && $height > 0 ) {
365 $this->metadata['width'] = intval( round( $width ) );
366 $this->metadata['height'] = intval( round( $height ) );
371 * Return a rounded pixel equivalent for a labeled CSS/SVG length.
372 * http://www.w3.org/TR/SVG11/coords.html#UnitIdentifiers
374 * @param string $length CSS/SVG length.
375 * @param float|int $viewportSize Optional scale for percentage units...
376 * @return float Length in pixels
378 static function scaleSVGUnit( $length, $viewportSize = 512 ) {
379 static $unitLength = [
380 'px' => 1.0,
381 'pt' => 1.25,
382 'pc' => 15.0,
383 'mm' => 3.543307,
384 'cm' => 35.43307,
385 'in' => 90.0,
386 'em' => 16.0, // fake it?
387 'ex' => 12.0, // fake it?
388 '' => 1.0, // "User units" pixels by default
390 $matches = [];
391 if ( preg_match( '/^\s*(\d+(?:\.\d+)?)(em|ex|px|pt|pc|cm|mm|in|%|)\s*$/', $length, $matches ) ) {
392 $length = floatval( $matches[1] );
393 $unit = $matches[2];
394 if ( $unit == '%' ) {
395 return $length * 0.01 * $viewportSize;
396 } else {
397 return $length * $unitLength[$unit];
399 } else {
400 // Assume pixels
401 return floatval( $length );