includes/Exif.php

   1 <?php
   2 if (defined('MEDIAWIKI')) {
   3 /**
   4  * @package MediaWiki
   5  * @subpackage Metadata
   6  *
   7  * @author Ævar Arnfjörð Bjarmason <avarab@gmail.com>
   8  * @copyright Copyright © 2005, Ævar Arnfjörð Bjarmason
   9  * @license http://www.gnu.org/copyleft/gpl.html GNU General Public License
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation; either version 2 of the License, or
  14  * (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License along
  22  * with this program; if not, write to the Free Software Foundation, Inc.,
  23  * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  24  * http://www.gnu.org/copyleft/gpl.html
  25  *
  26  * @link http://exif.org/Exif2-2.PDF The Exif 2.2 specification
  27  * @bug 1555, 1947
  28  */
  29
  30 /**
  31  * @package MediaWiki
  32  * @subpackage Metadata
  33  */
  34 class Exif {
  35         /**#@+
  36          * @var array
  37          */
  38
  39         /**
  40          * Exif tags grouped by category, the tagname itself is the key and the type
  41          * is the value, in the case of more than one possible value type they are
  42          * seperated by commas.
  43          *
  44          * @access private
  45          */
  46         var $mExif;
  47
  48         /**
  49          * A one dimentional array of all Exif tags
  50          */
  51         var $mFlatExif;
  52
  53         /**
  54          * A one dimentional array of all Exif tags that we'd want to save in
  55          * the database or present on a page.
  56          */
  57         var $mValidExif;
  58
  59         /**#@-*/
  60
  61         /**
  62          * Constructor
  63          */
  64         function Exif() {
  65                 /**#@+
  66                  * Exif tag type definition
  67                  */
  68                 define('BYTE', 1);              # An 8-bit unsigned integer.
  69                 define('ASCII', 2);             # An 8-bit byte containing one 7-bit ASCII code. The final byte is terminated with NULL.
  70                 define('SHORT', 3);             # A 16-bit (2-byte) unsigned integer.
  71                 define('LONG', 4);              # A 32-bit (4-byte) unsigned integer.
  72                 define('RATIONAL', 5);          # Two LONGs. The first LONG is the numerator and the second LONG expresses the denominator
  73                 define('UNDEFINED', 7);         # An 8-bit byte that can take any value depending on the field definition
  74                 define('SLONG', 9);             # A 32-bit (4-byte) signed integer (2's complement notation),
  75                 define('SRATIONAL', 10);        # Two SLONGs. The first SLONG is the numerator and the second SLONG is the denominator.
  76                 /**#@-*/
  77
  78                 /**
  79                  * Page numbers here refer to pages in the EXIF 2.2 standard
  80                  *
  81                  * @link http://exif.org/Exif2-2.PDF The Exif 2.2 specification
  82                  */
  83                 $this->mExif = array(
  84                         # TIFF Rev. 6.0 Attribute Information (p22)
  85                         'tiff' => array(
  86                                 # Tags relating to image structure
  87                                 'structure' => array(
  88                                         'ImageWidth' => SHORT.','.LONG,         # Image width
  89                                         'ImageLength' => SHORT.','.LONG,        # Image height
  90                                         'BitsPerSample' => SHORT,               # Number of bits per component
  91                                         # "When a primary image is JPEG compressed, this designation is not"
  92                                         # "necessary and is omitted." (p23)
  93                                         'Compression' => SHORT,                 # Compression scheme #p23
  94                                         'PhotometricInterpretation' => SHORT,   # Pixel composition #p23
  95                                         'Orientation' => SHORT,                 # Orientation of image #p24
  96                                         'SamplesPerPixel' => SHORT,             # Number of components
  97                                         'PlanarConfiguration' => SHORT,         # Image data arrangement #p24
  98                                         'YCbCrSubSampling' => SHORT,            # Subsampling ratio of Y to C #p24
  99                                         'YCbCrPositioning' => SHORT,            # Y and C positioning #p24-25
 100                                         'XResolution' => RATIONAL,              # Image resolution in width direction
 101                                         'YResolution' => RATIONAL,              # Image resolution in height direction
 102                                         'ResolutionUnit' => SHORT,              # Unit of X and Y resolution #(p26)
 103                                 ),
 104
 105                                 # Tags relating to recording offset
 106                                 'offset' => array(
 107                                         'StripOffsets' => SHORT.','.LONG,                       # Image data location
 108                                         'RowsPerStrip' => SHORT.','.LONG,                       # Number of rows per strip
 109                                         'StripByteCounts' => SHORT.','.LONG,                    # Bytes per compressed strip
 110                                         'JPEGInterchangeFormat' => SHORT.','.LONG,              # Offset to JPEG SOI
 111                                         'JPEGInterchangeFormatLength' => SHORT.','.LONG,        # Bytes of JPEG data
 112                                 ),
 113
 114                                 # Tags relating to image data characteristics
 115                                 'characteristics' => array(
 116                                         'TransferFunction' => SHORT,            # Transfer function
 117                                         'WhitePoint' => RATIONAL,               # White point chromaticity
 118                                         'PrimaryChromaticities' => RATIONAL,    # Chromaticities of primarities
 119                                         'YCbCrCoefficients' => RATIONAL,        # Color space transformation matrix coefficients #p27
 120                                         'ReferenceBlackWhite' => RATIONAL       # Pair of black and white reference values
 121                                 ),
 122
 123                                 # Other tags
 124                                 'other' => array(
 125                                         'DateTime' => ASCII,            # File change date and time
 126                                         'ImageDescription' => ASCII,    # Image title
 127                                         'Make' => ASCII,                # Image input equipment manufacturer
 128                                         'Model' => ASCII,               # Image input equipment model
 129                                         'Software' => ASCII,            # Software used
 130                                         'Artist' => ASCII,              # Person who created the image
 131                                         'Copyright' => ASCII,           # Copyright holder
 132                                 ),
 133                         ),
 134
 135                         # Exif IFD Attribute Information (p30-31)
 136                         'exif' => array(
 137                                 # Tags relating to version
 138                                 'version' => array(
 139                                         # TODO: NOTE: Nonexistence of this field is taken to mean nonconformance
 140                                         # to the EXIF 2.1 AND 2.2 standards
 141                                         'ExifVersion' => UNDEFINED,     # Exif version
 142                                         'FlashpixVersion' => UNDEFINED, # Supported Flashpix version #p32
 143                                 ),
 144
 145                                 # Tags relating to Image Data Characteristics
 146                                 'characteristics' => array(
 147                                         'ColorSpace' => SHORT,          # Color space information #p32
 148                                 ),
 149
 150                                 # Tags relating to image configuration
 151                                 'configuration' => array(
 152                                         'ComponentsConfiguration' => UNDEFINED,         # Meaning of each component #p33
 153                                         'CompressedBitsPerPixel' => RATIONAL,           # Image compression mode
 154                                         'PixelYDimension' => SHORT.','.LONG,            # Valid image width
 155                                         'PixelXDimension' => SHORT.','.LONG,            # Valind image height
 156                                 ),
 157
 158                                 # Tags relating to related user information
 159                                 'user' => array(
 160                                         'MakerNote' => UNDEFINED,                       # Manufacturer notes
 161                                         'UserComment' => UNDEFINED,                     # User comments #p34
 162                                 ),
 163
 164                                 # Tags relating to related file information
 165                                 'related' => array(
 166                                         'RelatedSoundFile' => ASCII,                    # Related audio file
 167                                 ),
 168
 169                                 # Tags relating to date and time
 170                                 'dateandtime' => array(
 171                                         'DateTimeOriginal' => ASCII,                    # Date and time of original data generation #p36
 172                                         'DateTimeDigitized' => ASCII,                   # Date and time of original data generation
 173                                         'SubSecTime' => ASCII,                          # DateTime subseconds
 174                                         'SubSecTimeOriginal' => ASCII,                  # DateTimeOriginal subseconds
 175                                         'SubSecTimeDigitized' => ASCII,                 # DateTimeDigitized subseconds
 176                                 ),
 177
 178                                 # Tags relating to picture-taking conditions (p31)
 179                                 'conditions' => array(
 180                                         'ExposureTime' => RATIONAL,                     # Exposure time
 181                                         'FNumber' => RATIONAL,                          # F Number
 182                                         'ExposureProgram' => SHORT,                     # Exposure Program #p38
 183                                         'SpectralSensitivity' => ASCII,                 # Spectral sensitivity
 184                                         'ISOSpeedRatings' => SHORT,                     # ISO speed rating
 185                                         'OECF' => UNDEFINED,                            # Optoelectronic conversion factor
 186                                         'ShutterSpeedValue' => SRATIONAL,               # Shutter speed
 187                                         'ApertureValue' => RATIONAL,                    # Aperture
 188                                         'BrightnessValue' => SRATIONAL,                 # Brightness
 189                                         'ExposureBiasValue' => SRATIONAL,               # Exposure bias
 190                                         'MaxApertureValue' => RATIONAL,                 # Maximum land aperture
 191                                         'SubjectDistance' => RATIONAL,                  # Subject distance
 192                                         'MeteringMode' => SHORT,                        # Metering mode #p40
 193                                         'LightSource' => SHORT,                         # Light source #p40-41
 194                                         'Flash' => SHORT,                               # Flash #p41-42
 195                                         'FocalLength' => RATIONAL,                      # Lens focal length
 196                                         'SubjectArea' => SHORT,                         # Subject area
 197                                         'FlashEnergy' => RATIONAL,                      # Flash energy
 198                                         'SpatialFrequencyResponse' => UNDEFINED,        # Spatial frequency response
 199                                         'FocalPlaneXResolution' => RATIONAL,            # Focal plane X resolution
 200                                         'FocalPlaneYResolution' => RATIONAL,            # Focal plane Y resolution
 201                                         'FocalPlaneResolutionUnit' => SHORT,            # Focal plane resolution unit
 202                                         'SubjectLocation' => SHORT,                     # Subject location
 203                                         'ExposureIndex' => RATIONAL,                    # Exposure index
 204                                         'SensingMethod' => SHORT,                       # Sensing method #p46
 205                                         'FileSource' => UNDEFINED,                      # File source #p47
 206                                         'SceneType' => UNDEFINED,                       # Scene type #p47
 207                                         'CFAPattern' => UNDEFINED,                      # CFA pattern
 208                                         'CustomRendered' => SHORT,                      # Custom image processing #p48
 209                                         'ExposureMode' => SHORT,                        # Exposure mode #p48
 210                                         'WhiteBalance' => SHORT,                        # White Balance #p49
 211                                         'DigitalZoomRatio' => RATIONAL,                 # Digital zoom ration
 212                                         'FocalLengthIn35mmFilm' => SHORT,               # Focal length in 35 mm film
 213                                         'SceneCaptureType' => SHORT,                    # Scene capture type #p49
 214                                         'GainControl' => RATIONAL,                      # Scene control #p49-50
 215                                         'Contrast' => SHORT,                            # Contrast #p50
 216                                         'Saturation' => SHORT,                          # Saturation #p50
 217                                         'Sharpness' => SHORT,                           # Sharpness #p50
 218                                         'DeviceSettingDescription' => UNDEFINED,        # Desice settings description
 219                                         'SubjectDistanceRange' => SHORT,                # Subject distance range #p51
 220                                 ),
 221
 222                                 'other' => array(
 223                                         'ImageUniqueID' => ASCII,       # Unique image ID
 224                                 ),
 225                         ),
 226
 227                         # GPS Attribute Information (p52)
 228                         'gps' => array(
 229                                 'GPSVersionID' => BYTE,                 # GPS tag version
 230                                 'GPSLatitudeRef' => ASCII,              # North or South Latitude #p52-53
 231                                 'GPSLatitude' => RATIONAL,              # Latitude
 232                                 'GPSLongitudeRef' => ASCII,             # East or West Longitude #p53
 233                                 'GPSLongitude' => RATIONAL,             # Longitude
 234                                 'GPSAltitudeRef' => BYTE,               # Altitude reference
 235                                 'GPSAltitude' => RATIONAL,              # Altitude
 236                                 'GPSTimeStamp' => RATIONAL,             # GPS time (atomic clock)
 237                                 'GPSSatellites' => ASCII,               # Satellites used for measurement
 238                                 'GPSStatus' => ASCII,                   # Receiver status #p54
 239                                 'GPSMeasureMode' => ASCII,              # Measurement mode #p54-55
 240                                 'GPSDOP' => RATIONAL,                   # Measurement precision
 241                                 'GPSSpeedRef' => ASCII,                 # Speed unit #p55
 242                                 'GPSSpeed' => RATIONAL,                 # Speed of GPS receiver
 243                                 'GPSTrackRef' => ASCII,                 # Reference for direction of movement #p55
 244                                 'GPSTrack' => RATIONAL,                 # Direction of movement
 245                                 'GPSImgDirectionRef' => ASCII,          # Reference for direction of image #p56
 246                                 'GPSImgDirection' => RATIONAL,          # Direction of image
 247                                 'GPSMapDatum' => ASCII,                 # Geodetic survey data used
 248                                 'GPSDestLatitudeRef' => ASCII,          # Reference for latitude of destination #p56
 249                                 'GPSDestLatitude' => RATIONAL,          # Latitude destination
 250                                 'GPSDestLongitudeRef' => ASCII,         # Reference for longitude of destination #p57
 251                                 'GPSDestLongitude' => RATIONAL,         # Longitude of destination
 252                                 'GPSDestBearingRef' => ASCII,           # Reference for bearing of destination #p57
 253                                 'GPSDestBearing' => RATIONAL,           # Bearing of destination
 254                                 'GPSDestDistanceRef' => ASCII,          # Reference for distance to destination #p57-58
 255                                 'GPSDestDistance' => RATIONAL,          # Distance to destination
 256                                 'GPSProcessingMethod' => UNDEFINED,     # Name of GPS processing method
 257                                 'GPSAreaInformation' => UNDEFINED,      # Name of GPS area
 258                                 'GPSDateStamp' => ASCII,                # GPS date
 259                                 'GPSDifferential' => SHORT,             # GPS differential correction
 260                         ),
 261                 );
 262
 263                 $this->makeFlatExifTags();
 264                 $this->makeValidExifTags();
 265         }
 266
 267         /**
 268          * Get the raw list of exiftags
 269          *
 270          * @access private
 271          * @return array
 272         */
 273         function getExif() {
 274                 return $this->mExif;
 275         }
 276
 277         /**
 278          * Generate a flat list of the exif tags
 279          */
 280         function makeFlatExifTags() {
 281                 $exif = $this->getExif();
 282                 $this->extractTags( $exif );
 283         }
 284
 285         /**
 286          * A recursing extractor function used by makeFlatExifTags()
 287          */
 288         function extractTags( $tagset ) {
 289                 foreach( $tagset as $key => $val ) {
 290                         if( is_array( $val ) ) {
 291                                 $this->extractTags( $val );
 292                         } else {
 293                                 $this->mFlatExif[$key] = $val;
 294                         }
 295                 }
 296         }
 297
 298         /**
 299          * Produce a list of all Exif tags appropriate for user output
 300          *
 301          * Produce a list of all tags that we want to show in output, in order not to
 302          * output binary gibberish such as raw thumbnails we strip all tags
 303          * with the datatype of UNDEFINED.
 304          *
 305          * @todo We might actually want to display some of the UNDEFINED
 306          *       stuff, but we strip it for now.
 307          */
 308         function makeValidExifTags() {
 309                 foreach($this->mFlatExif as $key => $val) {
 310                         if (strpos( $val, (string)UNDEFINED ) !== false)
 311                                 continue;
 312                         $this->mValidExif[] = $key;
 313                 }
 314         }
 315
 316          /**
 317           * The version of the output format
 318           *
 319           * Before the actual metadata information is saved in the database we
 320           * strip some of it since we don't want to save things like thumbnails
 321           * which usually accompany Exif data. This value gets saved in the
 322           * database along with the actual Exif data, and if the version in the
 323           * database doesn't equal the value returned by this function the Exif
 324           * data is regenerated.
 325           *
 326           * @return int
 327           */
 328         function version() {
 329                 return 1; // We don't need no bloddy constants!
 330         }
 331
 332         /**#@+
 333          * Validates if a tag value is of the type it should be according to the Exif spec
 334          *
 335          * @param mixed $in The input value to check
 336          * @return bool
 337          */
 338         function isByte( $in ) {
 339                 return is_numeric($in) && $in >= 0 && $in <= 255;
 340         }
 341
 342         function isASCII( $in ) {
 343                 return true; // TODO: FIXME
 344         }
 345
 346         function isShort( $in ) {
 347                 return is_numeric($in) && $in >= 0 && $in <= 65536;
 348         }
 349
 350         function isLong( $in ) {
 351                 return is_numeric($in) && $in >= 0 && $in <= 4294967296;
 352
 353         }
 354
 355         function isRational( $in ) {
 356                 $in = explode( '/', $in, 2 );
 357                 return $this->isLong($in[0]) && $this->isLong($in[1]);
 358         }
 359
 360         function isUndefined( $in ) {
 361                 return true;
 362         }
 363
 364         function isSlong( $in ) {
 365                 return $this->isLong( abs( $in ) );
 366         }
 367
 368         function isSrational( $in ) {
 369                 $in = explode( '/', $in, 2 );
 370                 return $this->isSlong($in[0]) && $this->isSlong($in[1]);
 371         }
 372         /**#@-*/
 373
 374         /**
 375          * Validates if a tag has a legal value according to the Exif spec, presumes
 376          * that the given tag is valid ( has been checked in advance with
 377          * $this->mValidExif )
 378          *
 379          * @param string $tag The tag to check
 380          * @param mixed  $val The value of the tag
 381          * @return bool
 382          */
 383         function validate( $tag, $val ) {
 384                 // Fucks up if not typecast
 385                 switch((string)$this->mFlatExif[$tag]) {
 386                         case (string)BYTE:
 387                                 return $this->isByte( $val );
 388                         case (string)ASCII:
 389                                 return $this->isASCII( $val );
 390                         case (string)SHORT:
 391                                 return $this->isShort( $val );
 392                         case (string)LONG:
 393                                 return $this->isLong( $val );
 394                         case (string)RATIONAL:
 395                                 return $this->isRational( $val );
 396                         case (string)UNDEFINED:
 397                                 return $this->isUndefined( $val );
 398                         case (string)SLONG:
 399                                 return $this->isSlong( $val );
 400                         case (string)SRATIONAL:
 401                                 return $this->isSrational( $val );
 402                         case (string)SHORT.','.LONG:
 403                                 return $this->isShort( $val ) || $this->isLong( $val );
 404                         default:
 405                                 wfDebug( "Exif: The tag \"$tag\" had an invalid value: \"$val\"\n" );
 406                                 return false;
 407                 }
 408         }
 409
 410         /**
 411          * Numbers given by Exif user agents are often magical, that is they
 412          * should be replaced by a detailed explanation depending on their
 413          * value which most of the time are plain integers. This function
 414          * formats Exif values into human readable form.
 415          *
 416          * @param string $tag The tag to be formatted
 417          * @param mixed  $val The value of the tag
 418          * @return string
 419          */
 420         function format( $tag, $val ) {
 421                 global $wgLang;
 422
 423                 switch ($tag) {
 424                         case 'Compression':
 425                                 switch ($val) {
 426                                         case 1: case 6:
 427                                                 return $this->msg( $tag, $val );
 428                                 }
 429
 430                         case 'PhotometricInterpretation':
 431                                 switch ($val) {
 432                                         case 2: case 6:
 433                                                 return $this->msg( $tag, $val );
 434                                 }
 435
 436                         case 'Orientation':
 437                                 switch ($val) {
 438                                         case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8:
 439                                                 return $this->msg( $tag, $val );
 440                                 }
 441
 442                         // TODO: If this field does not exist use 1
 443                         case 'PlanarConfiguration':
 444                                 switch ($val) {
 445                                         case 1: case 2:
 446                                                 return $this->msg( $tag, $val );
 447                                 }
 448
 449                         // TODO: YCbCrSubSampling
 450                         // TODO: YCbCrPositioning
 451                         // TODO: If this field does not exists use 2
 452                         case 'ResolutionUnit': #p26
 453                                 switch ($val) {
 454                                         case 2: case 3:
 455                                                 return $this->msg( $tag, $val );
 456                                 }
 457
 458                         // TODO: YCbCrCoefficients  #p27 (see annex E)
 459                         case 'ExifVersion': case 'FlashpixVersion':
 460                                 return "$val"/100;
 461
 462                         case 'ColorSpace':
 463                                 switch ($val) {
 464                                         case 1: case 'FFFF.H':
 465                                                 return $this->msg( $tag, $val );
 466                                 }
 467
 468                         case 'ComponentsConfiguration':
 469                                 switch ($val) {
 470                                         case 0: case 1: case 2: case 3: case 4: case 5: case 6:
 471                                                 return $this->msg( $tag, $val );
 472                                 }
 473
 474                         case 'DateTime':
 475                         case 'DateTimeOriginal':
 476                         case 'DateTimeDigitized':
 477                                 return $wgLang->timeanddate( wfTimestamp(TS_MW, $val) );
 478                         case 'ExposureProgram':
 479                                 switch ($val) {
 480                                         case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8:
 481                                                 return $this->msg( $tag, $val );
 482                                 }
 483                         case 'MeteringMode':
 484                                 switch ($val) {
 485                                         case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 255:
 486                                                 return $this->msg( $tag, $val );
 487                                 }
 488                         case 'LightSource':
 489                                 switch ($val) {
 490                                         case 0: case 1: case 2: case 3: case 4: case 9: case 10: case 11:
 491                                         case 12: case 13: case 14: case 15: case 17: case 18: case 19: case 20:
 492                                         case 21: case 22: case 23: case 24: case 255:
 493                                                 return $this->msg( $tag, $val );
 494                                 }
 495                         // TODO: Flash
 496                         case 'SensingMethod':
 497                                 switch ($val) {
 498                                         case 1: case 2: case 3: case 4: case 5: case 7: case 8:
 499                                                 return $this->msg( $tag, $val );
 500                                 }
 501                         case 'FileSource':
 502                                 switch ($val) {
 503                                         case 3:
 504                                                 return $this->msg( $tag, $val );
 505                                 }
 506                         case 'SceneType':
 507                                 switch ($val) {
 508                                         case 1:
 509                                                 return $this->msg( $tag, $val );
 510                                 }
 511                         case 'CustomRendered':
 512                                 switch ($val) {
 513                                         case 0: case 1:
 514                                                 return $this->msg( $tag, $val );
 515                                 }
 516                         case 'ExposureMode':
 517                                 switch ($val) {
 518                                         case 0: case 1: case 2:
 519                                                 return $this->msg( $tag, $val );
 520                                 }
 521                         case 'WhiteBalance':
 522                                 switch ($val) {
 523                                         case 0: case 1:
 524                                                 return $this->msg( $tag, $val );
 525                                 }
 526                         case 'SceneCaptureType':
 527                                 switch ($val) {
 528                                         case 0: case 1: case 2: case 3:
 529                                                 return $this->msg( $tag, $val );
 530                                 }
 531                         case 'GainControl':
 532                                 switch ($val) {
 533                                         case 0: case 1: case 2: case 3: case 4:
 534                                                 return $this->msg( $tag, $val );
 535                                 }
 536                         case 'Contrast':
 537                                 switch ($val) {
 538                                         case 0: case 1: case 2:
 539                                                 return $this->msg( $tag, $val );
 540                                 }
 541                         case 'Saturation':
 542                                 switch ($val) {
 543                                         case 0: case 1: case 2:
 544                                                 return $this->msg( $tag, $val );
 545                                 }
 546                         case 'Sharpness':
 547                                 switch ($val) {
 548                                         case 0: case 1: case 2:
 549                                                 return $this->msg( $tag, $val );
 550                                 }
 551                         case 'SubjectDistanceRange':
 552                                 switch ($val) {
 553                                         case 0: case 1: case 2: case 3:
 554                                                 return $this->msg( $tag, $val );
 555                                 }
 556                         case 'GPSLatitudeRef':
 557                                 switch ($val) {
 558                                         case 'N': case 'S':
 559                                                 return $this->msg( $tag, $val );
 560                                 }
 561                         case 'GPSLongitudeRef':
 562                                 switch ($val) {
 563                                         case 'E': case 'W':
 564                                                 return $this->msg( $tag, $val );
 565                                 }
 566                         case 'GPSStatus':
 567                                 switch ($val) {
 568                                         case 'A': case 'V':
 569                                                 return $this->msg( $tag, $val );
 570                                 }
 571                         case 'GPSMeasureMode':
 572                                 switch ($val) {
 573                                         case 2: case 3:
 574                                                 return $this->msg( $tag, $val );
 575                                 }
 576                         case 'GPSSpeedRef':
 577                                 switch ($val) {
 578                                         case 'K': case 'M': case 'N':
 579                                                 return $this->msg( $tag, $val );
 580                                 }
 581                         case 'GPSTrackRef':
 582                                 switch ($val) {
 583                                         case 'T': case 'M':
 584                                                 return $this->msg( $tag, $val );
 585                                 }
 586                         case 'GPSImgDirectionRef':
 587                                 switch ($val) {
 588                                         case 'T': case 'M':
 589                                                 return $this->msg( $tag, $val );
 590                                 }
 591                         case 'GPSDestLatitudeRef':
 592                                 switch ($val) {
 593                                         case 'N': case 'S':
 594                                                 return $this->msg( $tag, $val );
 595                                 }
 596                         case 'GPSDestLongitudeRef':
 597                                 switch ($val) {
 598                                         case 'E': case 'W':
 599                                                 return $this->msg( $tag, $val );
 600                                 }
 601                         case 'GPSDestBearingRef':
 602                                 switch ($val) {
 603                                         case 'T': case 'M':
 604                                                 return $this->msg( $tag, $val );
 605                                 }
 606                         case 'GPSDateStamp':
 607                                 return $wgLang->date( substr($val, 0, 4) . substr($val, 5, 2) . substr($val, 8, 2) . 000000 );
 608
 609                         // This is not in the Exif standard, just a special
 610                         // case for our purposes which enables wikis to wikify
 611                         // the make and model to write articles about them.
 612                         case 'Make': case 'Model':
 613                                 return wfMsg( strtolower( "exif-$tag-value" ), $val );
 614                         default:
 615                                 return $val;
 616                 }
 617         }
 618
 619         /**
 620          * Conviniance function for format()
 621          *
 622          * @param string $tag The tag name to pass on
 623          * @param string $val The value of the tag
 624          * @return string A wfMsg of "exif-$tag-$val" in lower case
 625          */
 626         function msg( $tag, $val ) {
 627                 return wfMsg( strtolower("exif-$tag-$val") );
 628         }
 629 }
 630 } // MEDIAWIKI