PHPSessionHandler: Implement SessionHandlerInterface

[mediawiki.git] / includes / media / Exif.php

<?php
/**
 * Extraction and validation of 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
 *
 * @ingroup Media
 * @author Ævar Arnfjörð Bjarmason <avarab@gmail.com>
 * @copyright Copyright © 2005, Ævar Arnfjörð Bjarmason, 2009 Brent Garber
 * @license http://www.gnu.org/copyleft/gpl.html GNU General Public License
 * @see http://exif.org/Exif2-2.PDF The Exif 2.2 specification
 * @file
 */

/**
 * Class to extract and validate Exif data from jpeg (and possibly tiff) files.
 * @ingroup Media
 */
class Exif {
        /** An 8-bit (1-byte) unsigned integer. */
        const BYTE = 1;

        /** An 8-bit byte containing one 7-bit ASCII code.
         *  The final byte is terminated with NULL.
         */
        const ASCII = 2;

        /** A 16-bit (2-byte) unsigned integer. */
        const SHORT = 3;

        /** A 32-bit (4-byte) unsigned integer. */
        const LONG = 4;

        /** Two LONGs. The first LONG is the numerator and the second LONG expresses
         *  the denominator
         */
        const RATIONAL = 5;

        /** A 16-bit (2-byte) or 32-bit (4-byte) unsigned integer. */
        const SHORT_OR_LONG = 6;

        /** An 8-bit byte that can take any value depending on the field definition */
        const UNDEFINED = 7;

        /** A 32-bit (4-byte) signed integer (2's complement notation), */
        const SLONG = 9;

        /** Two SLONGs. The first SLONG is the numerator and the second SLONG is
         *  the denominator.
         */
        const SRATIONAL = 10;

        /** A fake value for things we don't want or don't support. */
        const IGNORE = -1;

        /** @var array Exif tags grouped by category, the tagname itself is the key
         *    and the type is the value, in the case of more than one possible value
         *    type they are separated by commas.
         */
        private $mExifTags;

        /** @var array The raw Exif data returned by exif_read_data() */
        private $mRawExifData;

        /** @var array A Filtered version of $mRawExifData that has been pruned
         *    of invalid tags and tags that contain content they shouldn't contain
         *    according to the Exif specification
         */
        private $mFilteredExifData;

        /** @var string The file being processed */
        private $file;

        /** @var string The basename of the file being processed */
        private $basename;

        /** @var string The private log to log to, e.g. 'exif' */
        private $log = false;

        /** @var string The byte order of the file. Needed because php's extension
         *    doesn't fully process some obscure props.
         */
        private $byteOrder;

        /**
         * Constructor
         *
         * @param string $file Filename.
         * @param string $byteOrder Type of byte ordering either 'BE' (Big Endian)
         *   or 'LE' (Little Endian). Default ''.
         * @throws MWException
         * @todo FIXME: The following are broke:
         *   SubjectArea. Need to test the more obscure tags.
         *   DigitalZoomRatio = 0/0 is rejected. need to determine if that's valid.
         *   Possibly should treat 0/0 = 0. need to read exif spec on that.
         */
        function __construct( $file, $byteOrder = '' ) {
                /**
                 * Page numbers here refer to pages in the Exif 2.2 standard
                 *
                 * Note, Exif::UNDEFINED is treated as a string, not as an array of bytes
                 * so don't put a count parameter for any UNDEFINED values.
                 *
                 * @link http://exif.org/Exif2-2.PDF The Exif 2.2 specification
                 */
                $this->mExifTags = array(
                        # TIFF Rev. 6.0 Attribute Information (p22)
                        'IFD0' => array(
                                # Tags relating to image structure
                                'ImageWidth' => Exif::SHORT_OR_LONG, # Image width
                                'ImageLength' => Exif::SHORT_OR_LONG, # Image height
                                'BitsPerSample' => array( Exif::SHORT, 3 ), # Number of bits per component
                                # "When a primary image is JPEG compressed, this designation is not"
                                # "necessary and is omitted." (p23)
                                'Compression' => Exif::SHORT, # Compression scheme #p23
                                'PhotometricInterpretation' => Exif::SHORT, # Pixel composition #p23
                                'Orientation' => Exif::SHORT, # Orientation of image #p24
                                'SamplesPerPixel' => Exif::SHORT, # Number of components
                                'PlanarConfiguration' => Exif::SHORT, # Image data arrangement #p24
                                'YCbCrSubSampling' => array( Exif::SHORT, 2 ), # Subsampling ratio of Y to C #p24
                                'YCbCrPositioning' => Exif::SHORT, # Y and C positioning #p24-25
                                'XResolution' => Exif::RATIONAL, # Image resolution in width direction
                                'YResolution' => Exif::RATIONAL, # Image resolution in height direction
                                'ResolutionUnit' => Exif::SHORT, # Unit of X and Y resolution #(p26)

                                # Tags relating to recording offset
                                'StripOffsets' => Exif::SHORT_OR_LONG, # Image data location
                                'RowsPerStrip' => Exif::SHORT_OR_LONG, # Number of rows per strip
                                'StripByteCounts' => Exif::SHORT_OR_LONG, # Bytes per compressed strip
                                'JPEGInterchangeFormat' => Exif::SHORT_OR_LONG, # Offset to JPEG SOI
                                'JPEGInterchangeFormatLength' => Exif::SHORT_OR_LONG, # Bytes of JPEG data

                                # Tags relating to image data characteristics
                                'TransferFunction' => Exif::IGNORE, # Transfer function
                                'WhitePoint' => array( Exif::RATIONAL, 2 ), # White point chromaticity
                                'PrimaryChromaticities' => array( Exif::RATIONAL, 6 ), # Chromaticities of primarities
                                # Color space transformation matrix coefficients #p27
                                'YCbCrCoefficients' => array( Exif::RATIONAL, 3 ),
                                'ReferenceBlackWhite' => array( Exif::RATIONAL, 6 ), # Pair of black and white reference values

                                # Other tags
                                'DateTime' => Exif::ASCII, # File change date and time
                                'ImageDescription' => Exif::ASCII, # Image title
                                'Make' => Exif::ASCII, # Image input equipment manufacturer
                                'Model' => Exif::ASCII, # Image input equipment model
                                'Software' => Exif::ASCII, # Software used
                                'Artist' => Exif::ASCII, # Person who created the image
                                'Copyright' => Exif::ASCII, # Copyright holder
                        ),

                        # Exif IFD Attribute Information (p30-31)
                        'EXIF' => array(
                                # @todo NOTE: Nonexistence of this field is taken to mean nonconformance
                                # to the Exif 2.1 AND 2.2 standards
                                'ExifVersion' => Exif::UNDEFINED, # Exif version
                                'FlashPixVersion' => Exif::UNDEFINED, # Supported Flashpix version #p32

                                # Tags relating to Image Data Characteristics
                                'ColorSpace' => Exif::SHORT, # Color space information #p32

                                # Tags relating to image configuration
                                'ComponentsConfiguration' => Exif::UNDEFINED, # Meaning of each component #p33
                                'CompressedBitsPerPixel' => Exif::RATIONAL, # Image compression mode
                                'PixelYDimension' => Exif::SHORT_OR_LONG, # Valid image width
                                'PixelXDimension' => Exif::SHORT_OR_LONG, # Valid image height

                                # Tags relating to related user information
                                'MakerNote' => Exif::IGNORE, # Manufacturer notes
                                'UserComment' => Exif::UNDEFINED, # User comments #p34

                                # Tags relating to related file information
                                'RelatedSoundFile' => Exif::ASCII, # Related audio file

                                # Tags relating to date and time
                                'DateTimeOriginal' => Exif::ASCII, # Date and time of original data generation #p36
                                'DateTimeDigitized' => Exif::ASCII, # Date and time of original data generation
                                'SubSecTime' => Exif::ASCII, # DateTime subseconds
                                'SubSecTimeOriginal' => Exif::ASCII, # DateTimeOriginal subseconds
                                'SubSecTimeDigitized' => Exif::ASCII, # DateTimeDigitized subseconds

                                # Tags relating to picture-taking conditions (p31)
                                'ExposureTime' => Exif::RATIONAL, # Exposure time
                                'FNumber' => Exif::RATIONAL, # F Number
                                'ExposureProgram' => Exif::SHORT, # Exposure Program #p38
                                'SpectralSensitivity' => Exif::ASCII, # Spectral sensitivity
                                'ISOSpeedRatings' => Exif::SHORT, # ISO speed rating
                                'OECF' => Exif::IGNORE,
                                # Optoelectronic conversion factor. Note: We don't have support for this atm.
                                'ShutterSpeedValue' => Exif::SRATIONAL, # Shutter speed
                                'ApertureValue' => Exif::RATIONAL, # Aperture
                                'BrightnessValue' => Exif::SRATIONAL, # Brightness
                                'ExposureBiasValue' => Exif::SRATIONAL, # Exposure bias
                                'MaxApertureValue' => Exif::RATIONAL, # Maximum land aperture
                                'SubjectDistance' => Exif::RATIONAL, # Subject distance
                                'MeteringMode' => Exif::SHORT, # Metering mode #p40
                                'LightSource' => Exif::SHORT, # Light source #p40-41
                                'Flash' => Exif::SHORT, # Flash #p41-42
                                'FocalLength' => Exif::RATIONAL, # Lens focal length
                                'SubjectArea' => array( Exif::SHORT, 4 ), # Subject area
                                'FlashEnergy' => Exif::RATIONAL, # Flash energy
                                'SpatialFrequencyResponse' => Exif::IGNORE, # Spatial frequency response. Not supported atm.
                                'FocalPlaneXResolution' => Exif::RATIONAL, # Focal plane X resolution
                                'FocalPlaneYResolution' => Exif::RATIONAL, # Focal plane Y resolution
                                'FocalPlaneResolutionUnit' => Exif::SHORT, # Focal plane resolution unit #p46
                                'SubjectLocation' => array( Exif::SHORT, 2 ), # Subject location
                                'ExposureIndex' => Exif::RATIONAL, # Exposure index
                                'SensingMethod' => Exif::SHORT, # Sensing method #p46
                                'FileSource' => Exif::UNDEFINED, # File source #p47
                                'SceneType' => Exif::UNDEFINED, # Scene type #p47
                                'CFAPattern' => Exif::IGNORE, # CFA pattern. not supported atm.
                                'CustomRendered' => Exif::SHORT, # Custom image processing #p48
                                'ExposureMode' => Exif::SHORT, # Exposure mode #p48
                                'WhiteBalance' => Exif::SHORT, # White Balance #p49
                                'DigitalZoomRatio' => Exif::RATIONAL, # Digital zoom ration
                                'FocalLengthIn35mmFilm' => Exif::SHORT, # Focal length in 35 mm film
                                'SceneCaptureType' => Exif::SHORT, # Scene capture type #p49
                                'GainControl' => Exif::SHORT, # Scene control #p49-50
                                'Contrast' => Exif::SHORT, # Contrast #p50
                                'Saturation' => Exif::SHORT, # Saturation #p50
                                'Sharpness' => Exif::SHORT, # Sharpness #p50
                                'DeviceSettingDescription' => Exif::IGNORE,
                                # Device settings description. This could maybe be supported. Need to find an
                                # example file that uses this to see if it has stuff of interest in it.
                                'SubjectDistanceRange' => Exif::SHORT, # Subject distance range #p51

                                'ImageUniqueID' => Exif::ASCII, # Unique image ID
                        ),

                        # GPS Attribute Information (p52)
                        'GPS' => array(
                                'GPSVersion' => Exif::UNDEFINED,
                                # Should be an array of 4 Exif::BYTE's. However php treats it as an undefined
                                # Note exif standard calls this GPSVersionID, but php doesn't like the id suffix
                                'GPSLatitudeRef' => Exif::ASCII, # North or South Latitude #p52-53
                                'GPSLatitude' => array( Exif::RATIONAL, 3 ), # Latitude
                                'GPSLongitudeRef' => Exif::ASCII, # East or West Longitude #p53
                                'GPSLongitude' => array( Exif::RATIONAL, 3 ), # Longitude
                                'GPSAltitudeRef' => Exif::UNDEFINED,
                                # Altitude reference. Note, the exif standard says this should be an EXIF::Byte,
                                # but php seems to disagree.
                                'GPSAltitude' => Exif::RATIONAL, # Altitude
                                'GPSTimeStamp' => array( Exif::RATIONAL, 3 ), # GPS time (atomic clock)
                                'GPSSatellites' => Exif::ASCII, # Satellites used for measurement
                                'GPSStatus' => Exif::ASCII, # Receiver status #p54
                                'GPSMeasureMode' => Exif::ASCII, # Measurement mode #p54-55
                                'GPSDOP' => Exif::RATIONAL, # Measurement precision
                                'GPSSpeedRef' => Exif::ASCII, # Speed unit #p55
                                'GPSSpeed' => Exif::RATIONAL, # Speed of GPS receiver
                                'GPSTrackRef' => Exif::ASCII, # Reference for direction of movement #p55
                                'GPSTrack' => Exif::RATIONAL, # Direction of movement
                                'GPSImgDirectionRef' => Exif::ASCII, # Reference for direction of image #p56
                                'GPSImgDirection' => Exif::RATIONAL, # Direction of image
                                'GPSMapDatum' => Exif::ASCII, # Geodetic survey data used
                                'GPSDestLatitudeRef' => Exif::ASCII, # Reference for latitude of destination #p56
                                'GPSDestLatitude' => array( Exif::RATIONAL, 3 ), # Latitude destination
                                'GPSDestLongitudeRef' => Exif::ASCII, # Reference for longitude of destination #p57
                                'GPSDestLongitude' => array( Exif::RATIONAL, 3 ), # Longitude of destination
                                'GPSDestBearingRef' => Exif::ASCII, # Reference for bearing of destination #p57
                                'GPSDestBearing' => Exif::RATIONAL, # Bearing of destination
                                'GPSDestDistanceRef' => Exif::ASCII, # Reference for distance to destination #p57-58
                                'GPSDestDistance' => Exif::RATIONAL, # Distance to destination
                                'GPSProcessingMethod' => Exif::UNDEFINED, # Name of GPS processing method
                                'GPSAreaInformation' => Exif::UNDEFINED, # Name of GPS area
                                'GPSDateStamp' => Exif::ASCII, # GPS date
                                'GPSDifferential' => Exif::SHORT, # GPS differential correction
                        ),
                );

                $this->file = $file;
                $this->basename = wfBaseName( $this->file );
                if ( $byteOrder === 'BE' || $byteOrder === 'LE' ) {
                        $this->byteOrder = $byteOrder;
                } else {
                        // Only give a warning for b/c, since originally we didn't
                        // require this. The number of things affected by this is
                        // rather small.
                        wfWarn( 'Exif class did not have byte order specified. ' .
                                'Some properties may be decoded incorrectly.' );
                        $this->byteOrder = 'BE'; // BE seems about twice as popular as LE in jpg's.
                }

                $this->debugFile( $this->basename, __FUNCTION__, true );
                if ( function_exists( 'exif_read_data' ) ) {
                        MediaWiki\suppressWarnings();
                        $data = exif_read_data( $this->file, 0, true );
                        MediaWiki\restoreWarnings();
                } else {
                        throw new MWException( "Internal error: exif_read_data not present. " .
                                "\$wgShowEXIF may be incorrectly set or not checked by an extension." );
                }
                /**
                 * exif_read_data() will return false on invalid input, such as
                 * when somebody uploads a file called something.jpeg
                 * containing random gibberish.
                 */
                $this->mRawExifData = $data ?: array();
                $this->makeFilteredData();
                $this->collapseData();
                $this->debugFile( __FUNCTION__, false );
        }

        /**
         * Make $this->mFilteredExifData
         */
        function makeFilteredData() {
                $this->mFilteredExifData = array();

                foreach ( array_keys( $this->mRawExifData ) as $section ) {
                        if ( !array_key_exists( $section, $this->mExifTags ) ) {
                                $this->debug( $section, __FUNCTION__, "'$section' is not a valid Exif section" );
                                continue;
                        }

                        foreach ( array_keys( $this->mRawExifData[$section] ) as $tag ) {
                                if ( !array_key_exists( $tag, $this->mExifTags[$section] ) ) {
                                        $this->debug( $tag, __FUNCTION__, "'$tag' is not a valid tag in '$section'" );
                                        continue;
                                }

                                $this->mFilteredExifData[$tag] = $this->mRawExifData[$section][$tag];
                                // This is ok, as the tags in the different sections do not conflict.
                                // except in computed and thumbnail section, which we don't use.

                                $value = $this->mRawExifData[$section][$tag];
                                if ( !$this->validate( $section, $tag, $value ) ) {
                                        $this->debug( $value, __FUNCTION__, "'$tag' contained invalid data" );
                                        unset( $this->mFilteredExifData[$tag] );
                                }
                        }
                }
        }

        /**
         * Collapse some fields together.
         * This converts some fields from exif form, to a more friendly form.
         * For example GPS latitude to a single number.
         *
         * The rationale behind this is that we're storing data, not presenting to the user
         * For example a longitude is a single number describing how far away you are from
         * the prime meridian. Well it might be nice to split it up into minutes and seconds
         * for the user, it doesn't really make sense to split a single number into 4 parts
         * for storage. (degrees, minutes, second, direction vs single floating point number).
         *
         * Other things this might do (not really sure if they make sense or not):
         * Dates -> mediawiki date format.
         * convert values that can be in different units to be in one standardized unit.
         *
         * As an alternative approach, some of this could be done in the validate phase
         * if we make up our own types like Exif::DATE.
         */
        function collapseData() {

                $this->exifGPStoNumber( 'GPSLatitude' );
                $this->exifGPStoNumber( 'GPSDestLatitude' );
                $this->exifGPStoNumber( 'GPSLongitude' );
                $this->exifGPStoNumber( 'GPSDestLongitude' );

                if ( isset( $this->mFilteredExifData['GPSAltitude'] )
                        && isset( $this->mFilteredExifData['GPSAltitudeRef'] )
                ) {
                        // We know altitude data is a <num>/<denom> from the validation
                        // functions ran earlier. But multiplying such a string by -1
                        // doesn't work well, so convert.
                        list( $num, $denom ) = explode( '/', $this->mFilteredExifData['GPSAltitude'] );
                        $this->mFilteredExifData['GPSAltitude'] = $num / $denom;

                        if ( $this->mFilteredExifData['GPSAltitudeRef'] === "\1" ) {
                                $this->mFilteredExifData['GPSAltitude'] *= -1;
                        }
                        unset( $this->mFilteredExifData['GPSAltitudeRef'] );
                }

                $this->exifPropToOrd( 'FileSource' );
                $this->exifPropToOrd( 'SceneType' );

                $this->charCodeString( 'UserComment' );
                $this->charCodeString( 'GPSProcessingMethod' );
                $this->charCodeString( 'GPSAreaInformation' );

                // ComponentsConfiguration should really be an array instead of a string...
                // This turns a string of binary numbers into an array of numbers.

                if ( isset( $this->mFilteredExifData['ComponentsConfiguration'] ) ) {
                        $val = $this->mFilteredExifData['ComponentsConfiguration'];
                        $ccVals = array();

                        $strLen = strlen( $val );
                        for ( $i = 0; $i < $strLen; $i++ ) {
                                $ccVals[$i] = ord( substr( $val, $i, 1 ) );
                        }
                        $ccVals['_type'] = 'ol'; // this is for formatting later.
                        $this->mFilteredExifData['ComponentsConfiguration'] = $ccVals;
                }

                // GPSVersion(ID) is treated as the wrong type by php exif support.
                // Go through each byte turning it into a version string.
                // For example: "\x02\x02\x00\x00" -> "2.2.0.0"

                // Also change exif tag name from GPSVersion (what php exif thinks it is)
                // to GPSVersionID (what the exif standard thinks it is).

                if ( isset( $this->mFilteredExifData['GPSVersion'] ) ) {
                        $val = $this->mFilteredExifData['GPSVersion'];
                        $newVal = '';

                        $strLen = strlen( $val );
                        for ( $i = 0; $i < $strLen; $i++ ) {
                                if ( $i !== 0 ) {
                                        $newVal .= '.';
                                }
                                $newVal .= ord( substr( $val, $i, 1 ) );
                        }

                        if ( $this->byteOrder === 'LE' ) {
                                // Need to reverse the string
                                $newVal2 = '';
                                for ( $i = strlen( $newVal ) - 1; $i >= 0; $i-- ) {
                                        $newVal2 .= substr( $newVal, $i, 1 );
                                }
                                $this->mFilteredExifData['GPSVersionID'] = $newVal2;
                        } else {
                                $this->mFilteredExifData['GPSVersionID'] = $newVal;
                        }
                        unset( $this->mFilteredExifData['GPSVersion'] );
                }
        }

        /**
         * Do userComment tags and similar. See pg. 34 of exif standard.
         * basically first 8 bytes is charset, rest is value.
         * This has not been tested on any shift-JIS strings.
         * @param string $prop Prop name
         */
        private function charCodeString( $prop ) {
                if ( isset( $this->mFilteredExifData[$prop] ) ) {

                        if ( strlen( $this->mFilteredExifData[$prop] ) <= 8 ) {
                                // invalid. Must be at least 9 bytes long.

                                $this->debug( $this->mFilteredExifData[$prop], __FUNCTION__, false );
                                unset( $this->mFilteredExifData[$prop] );

                                return;
                        }
                        $charCode = substr( $this->mFilteredExifData[$prop], 0, 8 );
                        $val = substr( $this->mFilteredExifData[$prop], 8 );

                        switch ( $charCode ) {
                                case "\x4A\x49\x53\x00\x00\x00\x00\x00":
                                        // JIS
                                        $charset = "Shift-JIS";
                                        break;
                                case "UNICODE\x00":
                                        $charset = "UTF-16" . $this->byteOrder;
                                        break;
                                default: // ascii or undefined.
                                        $charset = "";
                                        break;
                        }
                        if ( $charset ) {
                                MediaWiki\suppressWarnings();
                                $val = iconv( $charset, 'UTF-8//IGNORE', $val );
                                MediaWiki\restoreWarnings();
                        } else {
                                // if valid utf-8, assume that, otherwise assume windows-1252
                                $valCopy = $val;
                                UtfNormal\Validator::quickIsNFCVerify( $valCopy ); // validates $valCopy.
                                if ( $valCopy !== $val ) {
                                        MediaWiki\suppressWarnings();
                                        $val = iconv( 'Windows-1252', 'UTF-8//IGNORE', $val );
                                        MediaWiki\restoreWarnings();
                                }
                        }

                        // trim and check to make sure not only whitespace.
                        $val = trim( $val );
                        if ( strlen( $val ) === 0 ) {
                                // only whitespace.
                                $this->debug( $this->mFilteredExifData[$prop], __FUNCTION__, "$prop: Is only whitespace" );
                                unset( $this->mFilteredExifData[$prop] );

                                return;
                        }

                        // all's good.
                        $this->mFilteredExifData[$prop] = $val;
                }
        }

        /**
         * Convert an Exif::UNDEFINED from a raw binary string
         * to its value. This is sometimes needed depending on
         * the type of UNDEFINED field
         * @param string $prop Name of property
         */
        private function exifPropToOrd( $prop ) {
                if ( isset( $this->mFilteredExifData[$prop] ) ) {
                        $this->mFilteredExifData[$prop] = ord( $this->mFilteredExifData[$prop] );
                }
        }

        /**
         * Convert gps in exif form to a single floating point number
         * for example 10 degress 20`40`` S -> -10.34444
         * @param string $prop A GPS coordinate exif tag name (like GPSLongitude)
         */
        private function exifGPStoNumber( $prop ) {
                $loc =& $this->mFilteredExifData[$prop];
                $dir =& $this->mFilteredExifData[$prop . 'Ref'];
                $res = false;

                if ( isset( $loc ) && isset( $dir )
                        && ( $dir === 'N' || $dir === 'S' || $dir === 'E' || $dir === 'W' )
                ) {
                        list( $num, $denom ) = explode( '/', $loc[0] );
                        $res = $num / $denom;
                        list( $num, $denom ) = explode( '/', $loc[1] );
                        $res += ( $num / $denom ) * ( 1 / 60 );
                        list( $num, $denom ) = explode( '/', $loc[2] );
                        $res += ( $num / $denom ) * ( 1 / 3600 );

                        if ( $dir === 'S' || $dir === 'W' ) {
                                $res *= -1; // make negative
                        }
                }

                // update the exif records.

                if ( $res !== false ) { // using !== as $res could potentially be 0
                        $this->mFilteredExifData[$prop] = $res;
                        unset( $this->mFilteredExifData[$prop . 'Ref'] );
                } else { // if invalid
                        unset( $this->mFilteredExifData[$prop] );
                        unset( $this->mFilteredExifData[$prop . 'Ref'] );
                }
        }

        /**#@-*/

        /**#@+
         * @return array
         */
        /**
         * Get $this->mRawExifData
         * @return array
         */
        function getData() {
                return $this->mRawExifData;
        }

        /**
         * Get $this->mFilteredExifData
         * @return array
         */
        function getFilteredData() {
                return $this->mFilteredExifData;
        }

        /**#@-*/

        /**
         * The version of the output format
         *
         * Before the actual metadata information is saved in the database we
         * strip some of it since we don't want to save things like thumbnails
         * which usually accompany Exif data. This value gets saved in the
         * database along with the actual Exif data, and if the version in the
         * database doesn't equal the value returned by this function the Exif
         * data is regenerated.
         *
         * @return int
         */
        public static function version() {
                return 2; // We don't need no bloddy constants!
        }

        /**
         * Validates if a tag value is of the type it should be according to the Exif spec
         *
         * @param mixed $in The input value to check
         * @return bool
         */
        private function isByte( $in ) {
                if ( !is_array( $in ) && sprintf( '%d', $in ) == $in && $in >= 0 && $in <= 255 ) {
                        $this->debug( $in, __FUNCTION__, true );

                        return true;
                } else {
                        $this->debug( $in, __FUNCTION__, false );

                        return false;
                }
        }

        /**
         * @param mixed $in The input value to check
         * @return bool
         */
        private function isASCII( $in ) {
                if ( is_array( $in ) ) {
                        return false;
                }

                if ( preg_match( "/[^\x0a\x20-\x7e]/", $in ) ) {
                        $this->debug( $in, __FUNCTION__, 'found a character not in our whitelist' );

                        return false;
                }

                if ( preg_match( '/^\s*$/', $in ) ) {
                        $this->debug( $in, __FUNCTION__, 'input consisted solely of whitespace' );

                        return false;
                }

                return true;
        }

        /**
         * @param mixed $in The input value to check
         * @return bool
         */
        private function isShort( $in ) {
                if ( !is_array( $in ) && sprintf( '%d', $in ) == $in && $in >= 0 && $in <= 65536 ) {
                        $this->debug( $in, __FUNCTION__, true );

                        return true;
                } else {
                        $this->debug( $in, __FUNCTION__, false );

                        return false;
                }
        }

        /**
         * @param mixed $in The input value to check
         * @return bool
         */
        private function isLong( $in ) {
                if ( !is_array( $in ) && sprintf( '%d', $in ) == $in && $in >= 0 && $in <= 4294967296 ) {
                        $this->debug( $in, __FUNCTION__, true );

                        return true;
                } else {
                        $this->debug( $in, __FUNCTION__, false );

                        return false;
                }
        }

        /**
         * @param mixed $in The input value to check
         * @return bool
         */
        private function isRational( $in ) {
                $m = array();

                # Avoid division by zero
                if ( !is_array( $in )
                        && preg_match( '/^(\d+)\/(\d+[1-9]|[1-9]\d*)$/', $in, $m )
                ) {
                        return $this->isLong( $m[1] ) && $this->isLong( $m[2] );
                } else {
                        $this->debug( $in, __FUNCTION__, 'fed a non-fraction value' );

                        return false;
                }
        }

        /**
         * @param mixed $in The input value to check
         * @return bool
         */
        private function isUndefined( $in ) {
                $this->debug( $in, __FUNCTION__, true );

                return true;
        }

        /**
         * @param mixed $in The input value to check
         * @return bool
         */
        private function isSlong( $in ) {
                if ( $this->isLong( abs( $in ) ) ) {
                        $this->debug( $in, __FUNCTION__, true );

                        return true;
                } else {
                        $this->debug( $in, __FUNCTION__, false );

                        return false;
                }
        }

        /**
         * @param mixed $in The input value to check
         * @return bool
         */
        private function isSrational( $in ) {
                $m = array();

                # Avoid division by zero
                if ( !is_array( $in ) &&
                        preg_match( '/^(-?\d+)\/(\d+[1-9]|[1-9]\d*)$/', $in, $m )
                ) {
                        return $this->isSlong( $m[0] ) && $this->isSlong( $m[1] );
                } else {
                        $this->debug( $in, __FUNCTION__, 'fed a non-fraction value' );

                        return false;
                }
        }

        /**#@-*/

        /**
         * Validates if a tag has a legal value according to the Exif spec
         *
         * @param string $section Section where tag is located.
         * @param string $tag The tag to check.
         * @param mixed $val The value of the tag.
         * @param bool $recursive True if called recursively for array types.
         * @return bool
         */
        private function validate( $section, $tag, $val, $recursive = false ) {
                $debug = "tag is '$tag'";
                $etype = $this->mExifTags[$section][$tag];
                $ecount = 1;
                if ( is_array( $etype ) ) {
                        list( $etype, $ecount ) = $etype;
                        if ( $recursive ) {
                                $ecount = 1; // checking individual elements
                        }
                }
                $count = count( $val );
                if ( $ecount != $count ) {
                        $this->debug( $val, __FUNCTION__, "Expected $ecount elements for $tag but got $count" );

                        return false;
                }
                if ( $count > 1 ) {
                        foreach ( $val as $v ) {
                                if ( !$this->validate( $section, $tag, $v, true ) ) {
                                        return false;
                                }
                        }

                        return true;
                }
                // Does not work if not typecast
                switch ( (string)$etype ) {
                        case (string)Exif::BYTE:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return $this->isByte( $val );
                        case (string)Exif::ASCII:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return $this->isASCII( $val );
                        case (string)Exif::SHORT:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return $this->isShort( $val );
                        case (string)Exif::LONG:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return $this->isLong( $val );
                        case (string)Exif::RATIONAL:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return $this->isRational( $val );
                        case (string)Exif::SHORT_OR_LONG:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return $this->isShort( $val ) || $this->isLong( $val );
                        case (string)Exif::UNDEFINED:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return $this->isUndefined( $val );
                        case (string)Exif::SLONG:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return $this->isSlong( $val );
                        case (string)Exif::SRATIONAL:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return $this->isSrational( $val );
                        case (string)Exif::IGNORE:
                                $this->debug( $val, __FUNCTION__, $debug );

                                return false;
                        default:
                                $this->debug( $val, __FUNCTION__, "The tag '$tag' is unknown" );

                                return false;
                }
        }

        /**
         * Convenience function for debugging output
         *
         * @param mixed $in Arrays will be processed with print_r().
         * @param string $fname Function name to log.
         * @param string|bool|null $action Default null.
         */
        private function debug( $in, $fname, $action = null ) {
                if ( !$this->log ) {
                        return;
                }
                $type = gettype( $in );
                $class = ucfirst( __CLASS__ );
                if ( is_array( $in ) ) {
                        $in = print_r( $in, true );
                }

                if ( $action === true ) {
                        wfDebugLog( $this->log, "$class::$fname: accepted: '$in' (type: $type)" );
                } elseif ( $action === false ) {
                        wfDebugLog( $this->log, "$class::$fname: rejected: '$in' (type: $type)" );
                } elseif ( $action === null ) {
                        wfDebugLog( $this->log, "$class::$fname: input was: '$in' (type: $type)" );
                } else {
                        wfDebugLog( $this->log, "$class::$fname: $action (type: $type; content: '$in')" );
                }
        }

        /**
         * Convenience function for debugging output
         *
         * @param string $fname The name of the function calling this function
         * @param bool $io Specify whether we're beginning or ending
         */
        private function debugFile( $fname, $io ) {
                if ( !$this->log ) {
                        return;
                }
                $class = ucfirst( __CLASS__ );
                if ( $io ) {
                        wfDebugLog( $this->log, "$class::$fname: begin processing: '{$this->basename}'" );
                } else {
                        wfDebugLog( $this->log, "$class::$fname: end processing: '{$this->basename}'" );
                }
        }
}