diff options
Diffstat (limited to 'www/wiki/includes/media/SVGMetadataExtractor.php')
| -rw-r--r-- | www/wiki/includes/media/SVGMetadataExtractor.php | 396 |
1 files changed, 396 insertions, 0 deletions
diff --git a/www/wiki/includes/media/SVGMetadataExtractor.php b/www/wiki/includes/media/SVGMetadataExtractor.php new file mode 100644 index 00000000..fc93b233 --- /dev/null +++ b/www/wiki/includes/media/SVGMetadataExtractor.php @@ -0,0 +1,396 @@ +<?php +/** + * Extraction of SVG image metadata. + * + * 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 + * + * @file + * @ingroup Media + * @author "Derk-Jan Hartman <hartman _at_ videolan d0t org>" + * @author Brion Vibber + * @copyright Copyright © 2010-2010 Brion Vibber, Derk-Jan Hartman + * @license http://www.gnu.org/copyleft/gpl.html GNU General Public License + */ + +/** + * @ingroup Media + */ +class SVGMetadataExtractor { + static function getMetadata( $filename ) { + $svg = new SVGReader( $filename ); + + return $svg->getMetadata(); + } +} + +/** + * @ingroup Media + */ +class SVGReader { + const DEFAULT_WIDTH = 512; + const DEFAULT_HEIGHT = 512; + const NS_SVG = 'http://www.w3.org/2000/svg'; + const LANG_PREFIX_MATCH = 1; + const LANG_FULL_MATCH = 2; + + /** @var null|XMLReader */ + private $reader = null; + + /** @var bool */ + private $mDebug = false; + + /** @var array */ + private $metadata = []; + private $languages = []; + private $languagePrefixes = []; + + /** + * Creates an SVGReader drawing from the source provided + * @param string $source URI from which to read + * @throws MWException|Exception + */ + function __construct( $source ) { + global $wgSVGMetadataCutoff; + $this->reader = new XMLReader(); + + // Don't use $file->getSize() since file object passed to SVGHandler::getMetadata is bogus. + $size = filesize( $source ); + if ( $size === false ) { + throw new MWException( "Error getting filesize of SVG." ); + } + + if ( $size > $wgSVGMetadataCutoff ) { + $this->debug( "SVG is $size bytes, which is bigger than $wgSVGMetadataCutoff. Truncating." ); + $contents = file_get_contents( $source, false, null, -1, $wgSVGMetadataCutoff ); + if ( $contents === false ) { + throw new MWException( 'Error reading SVG file.' ); + } + $this->reader->XML( $contents, null, LIBXML_NOERROR | LIBXML_NOWARNING ); + } else { + $this->reader->open( $source, null, LIBXML_NOERROR | LIBXML_NOWARNING ); + } + + // Expand entities, since Adobe Illustrator uses them for xmlns + // attributes (T33719). Note that libxml2 has some protection + // against large recursive entity expansions so this is not as + // insecure as it might appear to be. However, it is still extremely + // insecure. It's necessary to wrap any read() calls with + // libxml_disable_entity_loader() to avoid arbitrary local file + // inclusion, or even arbitrary code execution if the expect + // extension is installed (T48859). + $oldDisable = libxml_disable_entity_loader( true ); + $this->reader->setParserProperty( XMLReader::SUBST_ENTITIES, true ); + + $this->metadata['width'] = self::DEFAULT_WIDTH; + $this->metadata['height'] = self::DEFAULT_HEIGHT; + + // The size in the units specified by the SVG file + // (for the metadata box) + // Per the SVG spec, if unspecified, default to '100%' + $this->metadata['originalWidth'] = '100%'; + $this->metadata['originalHeight'] = '100%'; + + // Because we cut off the end of the svg making an invalid one. Complicated + // try catch thing to make sure warnings get restored. Seems like there should + // be a better way. + Wikimedia\suppressWarnings(); + try { + $this->read(); + } catch ( Exception $e ) { + // Note, if this happens, the width/height will be taken to be 0x0. + // Should we consider it the default 512x512 instead? + Wikimedia\restoreWarnings(); + libxml_disable_entity_loader( $oldDisable ); + throw $e; + } + Wikimedia\restoreWarnings(); + libxml_disable_entity_loader( $oldDisable ); + } + + /** + * @return array Array with the known metadata + */ + public function getMetadata() { + return $this->metadata; + } + + /** + * Read the SVG + * @throws MWException + * @return bool + */ + protected function read() { + $keepReading = $this->reader->read(); + + /* Skip until first element */ + while ( $keepReading && $this->reader->nodeType != XMLReader::ELEMENT ) { + $keepReading = $this->reader->read(); + } + + if ( $this->reader->localName != 'svg' || $this->reader->namespaceURI != self::NS_SVG ) { + throw new MWException( "Expected <svg> tag, got " . + $this->reader->localName . " in NS " . $this->reader->namespaceURI ); + } + $this->debug( "<svg> tag is correct." ); + $this->handleSVGAttribs(); + + $exitDepth = $this->reader->depth; + $keepReading = $this->reader->read(); + while ( $keepReading ) { + $tag = $this->reader->localName; + $type = $this->reader->nodeType; + $isSVG = ( $this->reader->namespaceURI == self::NS_SVG ); + + $this->debug( "$tag" ); + + if ( $isSVG && $tag == 'svg' && $type == XMLReader::END_ELEMENT + && $this->reader->depth <= $exitDepth + ) { + break; + } elseif ( $isSVG && $tag == 'title' ) { + $this->readField( $tag, 'title' ); + } elseif ( $isSVG && $tag == 'desc' ) { + $this->readField( $tag, 'description' ); + } elseif ( $isSVG && $tag == 'metadata' && $type == XMLReader::ELEMENT ) { + $this->readXml( $tag, 'metadata' ); + } elseif ( $isSVG && $tag == 'script' ) { + // We normally do not allow scripted svgs. + // However its possible to configure MW to let them + // in, and such files should be considered animated. + $this->metadata['animated'] = true; + } elseif ( $tag !== '#text' ) { + $this->debug( "Unhandled top-level XML tag $tag" ); + + // Recurse into children of current tag, looking for animation and languages. + $this->animateFilterAndLang( $tag ); + } + + // Goto next element, which is sibling of current (Skip children). + $keepReading = $this->reader->next(); + } + + $this->reader->close(); + + $this->metadata['translations'] = $this->languages + $this->languagePrefixes; + + return true; + } + + /** + * Read a textelement from an element + * + * @param string $name Name of the element that we are reading from + * @param string $metafield Field that we will fill with the result + */ + private function readField( $name, $metafield = null ) { + $this->debug( "Read field $metafield" ); + if ( !$metafield || $this->reader->nodeType != XMLReader::ELEMENT ) { + return; + } + $keepReading = $this->reader->read(); + while ( $keepReading ) { + if ( $this->reader->localName == $name + && $this->reader->namespaceURI == self::NS_SVG + && $this->reader->nodeType == XMLReader::END_ELEMENT + ) { + break; + } elseif ( $this->reader->nodeType == XMLReader::TEXT ) { + $this->metadata[$metafield] = trim( $this->reader->value ); + } + $keepReading = $this->reader->read(); + } + } + + /** + * Read an XML snippet from an element + * + * @param string $metafield Field that we will fill with the result + * @throws MWException + */ + private function readXml( $metafield = null ) { + $this->debug( "Read top level metadata" ); + if ( !$metafield || $this->reader->nodeType != XMLReader::ELEMENT ) { + return; + } + // @todo Find and store type of xml snippet. metadata['metadataType'] = "rdf" + if ( method_exists( $this->reader, 'readInnerXML' ) ) { + $this->metadata[$metafield] = trim( $this->reader->readInnerXml() ); + } else { + throw new MWException( "The PHP XMLReader extension does not come " . + "with readInnerXML() method. Your libxml is probably out of " . + "date (need 2.6.20 or later)." ); + } + $this->reader->next(); + } + + /** + * Filter all children, looking for animated elements. + * Also get a list of languages that can be targeted. + * + * @param string $name Name of the element that we are reading from + */ + private function animateFilterAndLang( $name ) { + $this->debug( "animate filter for tag $name" ); + if ( $this->reader->nodeType != XMLReader::ELEMENT ) { + return; + } + if ( $this->reader->isEmptyElement ) { + return; + } + $exitDepth = $this->reader->depth; + $keepReading = $this->reader->read(); + while ( $keepReading ) { + if ( $this->reader->localName == $name && $this->reader->depth <= $exitDepth + && $this->reader->nodeType == XMLReader::END_ELEMENT + ) { + break; + } elseif ( $this->reader->namespaceURI == self::NS_SVG + && $this->reader->nodeType == XMLReader::ELEMENT + ) { + $sysLang = $this->reader->getAttribute( 'systemLanguage' ); + if ( !is_null( $sysLang ) && $sysLang !== '' ) { + // See https://www.w3.org/TR/SVG/struct.html#SystemLanguageAttribute + $langList = explode( ',', $sysLang ); + foreach ( $langList as $langItem ) { + $langItem = trim( $langItem ); + if ( Language::isWellFormedLanguageTag( $langItem ) ) { + $this->languages[$langItem] = self::LANG_FULL_MATCH; + } + // Note, the standard says that any prefix should work, + // here we do only the initial prefix, since that will catch + // 99% of cases, and we are going to compare against fallbacks. + // This differs mildly from how the spec says languages should be + // handled, however it matches better how the MediaWiki language + // preference is generally handled. + $dash = strpos( $langItem, '-' ); + // Intentionally checking both !false and > 0 at the same time. + if ( $dash ) { + $itemPrefix = substr( $langItem, 0, $dash ); + if ( Language::isWellFormedLanguageTag( $itemPrefix ) ) { + $this->languagePrefixes[$itemPrefix] = self::LANG_PREFIX_MATCH; + } + } + } + } + switch ( $this->reader->localName ) { + case 'script': + // Normally we disallow files with + // <script>, but its possible + // to configure MW to disable + // such checks. + case 'animate': + case 'set': + case 'animateMotion': + case 'animateColor': + case 'animateTransform': + $this->debug( "HOUSTON WE HAVE ANIMATION" ); + $this->metadata['animated'] = true; + break; + } + } + $keepReading = $this->reader->read(); + } + } + + private function debug( $data ) { + if ( $this->mDebug ) { + wfDebug( "SVGReader: $data\n" ); + } + } + + /** + * Parse the attributes of an SVG element + * + * The parser has to be in the start element of "<svg>" + */ + private function handleSVGAttribs() { + $defaultWidth = self::DEFAULT_WIDTH; + $defaultHeight = self::DEFAULT_HEIGHT; + $aspect = 1.0; + $width = null; + $height = null; + + if ( $this->reader->getAttribute( 'viewBox' ) ) { + // min-x min-y width height + $viewBox = preg_split( '/\s+/', trim( $this->reader->getAttribute( 'viewBox' ) ) ); + if ( count( $viewBox ) == 4 ) { + $viewWidth = $this->scaleSVGUnit( $viewBox[2] ); + $viewHeight = $this->scaleSVGUnit( $viewBox[3] ); + if ( $viewWidth > 0 && $viewHeight > 0 ) { + $aspect = $viewWidth / $viewHeight; + $defaultHeight = $defaultWidth / $aspect; + } + } + } + if ( $this->reader->getAttribute( 'width' ) ) { + $width = $this->scaleSVGUnit( $this->reader->getAttribute( 'width' ), $defaultWidth ); + $this->metadata['originalWidth'] = $this->reader->getAttribute( 'width' ); + } + if ( $this->reader->getAttribute( 'height' ) ) { + $height = $this->scaleSVGUnit( $this->reader->getAttribute( 'height' ), $defaultHeight ); + $this->metadata['originalHeight'] = $this->reader->getAttribute( 'height' ); + } + + if ( !isset( $width ) && !isset( $height ) ) { + $width = $defaultWidth; + $height = $width / $aspect; + } elseif ( isset( $width ) && !isset( $height ) ) { + $height = $width / $aspect; + } elseif ( isset( $height ) && !isset( $width ) ) { + $width = $height * $aspect; + } + + if ( $width > 0 && $height > 0 ) { + $this->metadata['width'] = intval( round( $width ) ); + $this->metadata['height'] = intval( round( $height ) ); + } + } + + /** + * Return a rounded pixel equivalent for a labeled CSS/SVG length. + * https://www.w3.org/TR/SVG11/coords.html#Units + * + * @param string $length CSS/SVG length. + * @param float|int $viewportSize Optional scale for percentage units... + * @return float Length in pixels + */ + static function scaleSVGUnit( $length, $viewportSize = 512 ) { + static $unitLength = [ + 'px' => 1.0, + 'pt' => 1.25, + 'pc' => 15.0, + 'mm' => 3.543307, + 'cm' => 35.43307, + 'in' => 90.0, + 'em' => 16.0, // fake it? + 'ex' => 12.0, // fake it? + '' => 1.0, // "User units" pixels by default + ]; + $matches = []; + if ( preg_match( '/^\s*(\d+(?:\.\d+)?)(em|ex|px|pt|pc|cm|mm|in|%|)\s*$/', $length, $matches ) ) { + $length = floatval( $matches[1] ); + $unit = $matches[2]; + if ( $unit == '%' ) { + return $length * 0.01 * $viewportSize; + } else { + return $length * $unitLength[$unit]; + } + } else { + // Assume pixels + return floatval( $length ); + } + } +} |