<?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 {

	const BYTE = 1; //!< An 8-bit (1-byte) unsigned integer.
	const ASCII = 2; //!< An 8-bit byte containing one 7-bit ASCII code. The final byte is terminated with NULL.
	const SHORT = 3; //!< A 16-bit (2-byte) unsigned integer.
	const LONG = 4; //!< A 32-bit (4-byte) unsigned integer.
	const RATIONAL = 5; //!< Two LONGs. The first LONG is the numerator and the second LONG expresses the denominator
	const SHORT_OR_LONG = 6; //!< A 16-bit (2-byte) or 32-bit (4-byte) unsigned integer.
	const UNDEFINED = 7; //!< An 8-bit byte that can take any value depending on the field definition
	const SLONG = 9; //!< A 32-bit (4-byte) signed integer (2's complement notation),
	const SRATIONAL = 10; //!< Two SLONGs. The first SLONG is the numerator and the second SLONG is the denominator.
	const IGNORE = -1; // A fake value for things we don't want or don't support.

	//@{
	/* @var array
	 * @private
	 */

	/**
	 * 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.
	 */
	var $mExifTags;

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

	/**
	 * 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
	 */
	var $mFilteredExifData;

	/**
	 * Filtered and formatted Exif data, see FormatMetadata::getFormattedData()
	 */
	var $mFormattedExifData;

	//@}

	//@{
	/* @var string
	 * @private
	 */

	/**
	 * The file being processed
	 */
	var $file;

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

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

	/**
	 * 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
				'YCbCrCoefficients' => array( Exif::RATIONAL, 3 ),	# Color space transformation matrix coefficients #p27
				'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' ) ) {
			wfSuppressWarnings();
			$data = exif_read_data( $this->file, 0, true );
			wfRestoreWarnings();
		} 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 ? $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 ( !in_array( $section, array_keys( $this->mExifTags ) ) ) {
				$this->debug( $section, __FUNCTION__, "'$section' is not a valid Exif section" );
				continue;
			}

			foreach ( array_keys( $this->mRawExifData[$section] ) as $tag ) {
				if ( !in_array( $tag, array_keys( $this->mExifTags[$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();
			for ( $i = 0; $i < strlen( $val ); $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 = '';
			for ( $i = 0; $i < strlen( $val ); $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;
			}
			// This could possibly check to see if iconv is really installed
			// or if we're using the compatibility wrapper in globalFunctions.php
			if ( $charset ) {
				wfSuppressWarnings();
				$val = iconv( $charset, 'UTF-8//IGNORE', $val );
				wfRestoreWarnings();
			} else {
				// if valid utf-8, assume that, otherwise assume windows-1252
				$valCopy = $val;
				UtfNormal::quickIsNFCVerify( $valCopy ); //validates $valCopy.
				if ( $valCopy !== $val ) {
					wfSuppressWarnings();
					$val = iconv( 'Windows-1252', 'UTF-8//IGNORE', $val );
					wfRestoreWarnings();
				}
			}

			//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'] );
		}
	}

	/**
	 * Use FormatMetadata to create formatted values for display to user
	 * (is this ever used?)
	 *
	 * @deprecated since 1.18
	 */
	function makeFormattedData() {
		wfDeprecated( __METHOD__, '1.18' );
		$this->mFormattedExifData = FormatMetadata::getFormattedData(
			$this->mFilteredExifData );
	}
	/**#@-*/

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

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

	/**
	 * Get $this->mFormattedExifData
	 *
	 * This returns the data for display to user.
	 * Its unclear if this is ever used.
	 *
	 * @deprecated since 1.18
	 */
	function getFormattedData() {
		wfDeprecated( __METHOD__, '1.18' );
		if ( !$this->mFormattedExifData ) {
			$this->makeFormattedData();
		}
		return $this->mFormattedExifData;
	}
	/**#@-*/

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

	/**
	 * @param $in
	 * @return bool
	 */
	private function isUndefined( $in ) {
		$this->debug( $in, __FUNCTION__, true );
		return true;
	}

	/**
	 * @param $in
	 * @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 $in
	 * @return bool
	 */
	private function isSrational( $in ) {
		$m = array();
		if ( !is_array( $in ) && preg_match( '/^(-?\d+)\/(\d+[1-9]|[1-9]\d*)$/', $in, $m ) ) { # Avoid division by zero
			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
	 *
	 * @private
	 * @param string $section section where tag is located.
	 * @param string $tag the tag to check.
	 * @param $val Mixed: the value of the tag.
	 * @param $recursive Boolean: 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
	 *
	 * @private
	 *
	 * @param $in Mixed:
	 * @param $fname String:
	 * @param $action Mixed: , 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)\n" );
		} elseif ( $action === false ) {
			wfDebugLog( $this->log, "$class::$fname: rejected: '$in' (type: $type)\n" );
		} elseif ( $action === null ) {
			wfDebugLog( $this->log, "$class::$fname: input was: '$in' (type: $type)\n" );
		} else {
			wfDebugLog( $this->log, "$class::$fname: $action (type: $type; content: '$in')\n" );
		}
	}

	/**
	 * Convenience function for debugging output
	 *
	 * @private
	 *
	 * @param string $fname the name of the function calling this function
	 * @param $io Boolean: 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}'\n" );
		} else {
			wfDebugLog( $this->log, "$class::$fname: end processing: '{$this->basename}'\n" );
		}
	}
}