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 = $this->getExif();
 282                 array_walk($exif, array(&$this, 'callback')); // note the reference
 283         }
 284
 285         /**
 286          * A callback function used by makeFlatExifTags()
 287          */
 288         function callback($val, $key) {
 289                 if (gettype($val) === 'array')
 290                         array_walk($val, array(&$this, 'callback'));
 291                 else
 292                         $this->mFlatExif[$key] = $val;
 293         }
 294
 295         /**
 296          * Produce a list of all Exif tags appropriate for user output
 297          *
 298          * Produce a list of all tags that we want to show in output, in order not to
 299          * output binary gibberish such as raw thumbnails we strip all tags
 300          * with the datatype of UNDEFINED.
 301          *
 302          * @todo We might actually want to display some of the UNDEFINED
 303          *       stuff, but we strip it for now.
 304          */
 305         function makeValidExifTags() {
 306                 foreach($this->mFlatExif as $key => $val) {
 307                         if (strpos( $val, (string)UNDEFINED ) !== false)
 308                                 continue;
 309                         $this->mValidExif[] = $key;
 310                 }
 311         }
 312
 313          /**
 314           * The version of the output format
 315           *
 316           * Before the actual metadata information is saved in the database we
 317           * strip some of it since we don't want to save things like thumbnails
 318           * which usually accompany Exif data. This value gets saved in the
 319           * database along with the actual Exif data, and if the version in the
 320           * database doesn't equal the value returned by this function the Exif
 321           * data is regenerated.
 322           *
 323           * @return int
 324           */
 325         function version() {
 326                 return 1; // We don't need no bloddy constants!
 327         }
 328
 329         /**#@+
 330          * Validates if a tag value is of the type it should be according to the Exif spec
 331          *
 332          * @param mixed $in The input value to check
 333          * @return bool
 334          */
 335         function isByte( $in ) {
 336                 return is_numeric($in) && $in >= 0 && $in <= 255;
 337         }
 338
 339         function isASCII( $in ) {
 340                 return true; // TODO: FIXME
 341         }
 342
 343         function isShort( $in ) {
 344                 return is_numeric($in) && $in >= 0 && $in <= 65536;
 345         }
 346
 347         function isLong( $in ) {
 348                 return is_numeric($in) && $in >= 0 && $in <= 4294967296;
 349
 350         }
 351
 352         function isRational( $in ) {
 353                 $in = explode( '/', $in, 2 );
 354                 return $this->isLong($in[0]) && $this->isLong($in[1]);
 355         }
 356
 357         function isUndefined( $in ) {
 358                 return true;
 359         }
 360
 361         function isSlong( $in ) {
 362                 return $this->isLong( abs( $in ) );
 363         }
 364
 365         function isSrational( $in ) {
 366                 $in = explode( '/', $in, 2 );
 367                 return $this->isSlong($in[0]) && $this->isSlong($in[1]);
 368         }
 369         /**#@-*/
 370
 371         /**
 372          * Validates if a tag has a legal value according to the Exif spec, presumes
 373          * that the given tag is valid ( has been checked in advance with
 374          * $this->mValidExif )
 375          *
 376          * @param string $tag The tag to check
 377          * @param mixed  $val The value of the tag
 378          * @return bool
 379          */
 380         function validate( $tag, $val ) {
 381                 // Fucks up if not typecast
 382                 switch((string)$this->mFlatExif[$tag]) {
 383                         case (string)BYTE:
 384                                 return $this->isByte( $val );
 385                         case (string)ASCII:
 386                                 return $this->isASCII( $val );
 387                         case (string)SHORT:
 388                                 return $this->isShort( $val );
 389                         case (string)LONG:
 390                                 return $this->isLong( $val );
 391                         case (string)RATIONAL:
 392                                 return $this->isRational( $val );
 393                         case (string)UNDEFINED:
 394                                 return $this->isUndefined( $val );
 395                         case (string)SLONG:
 396                                 return $this->isSlong( $val );
 397                         case (string)SRATIONAL:
 398                                 return $this->isSrational( $val );
 399                         case (string)SHORT.','.LONG:
 400                                 return $this->isShort( $val ) || $this->isLong( $val );
 401                         default:
 402                                 wfDebug( "Exif: The tag \"$tag\" had an invalid value: \"$val\"\n" );
 403                                 return false;
 404                 }
 405         }
 406
 407         /**
 408          * Numbers given by Exif user agents are often magical, that is they
 409          * should be replaced by a detailed explanation depending on their
 410          * value which most of the time are plain integers. This function
 411          * formats Exif values into human readable form.
 412          *
 413          * @param string $tag The tag to be formatted
 414          * @param mixed  $val The value of the tag
 415          * @return string
 416          */
 417         function format( $tag, $val ) {
 418                 global $wgLang;
 419
 420                 switch ($tag) {
 421                         case 'Compression':
 422                                 switch ($val) {
 423                                         case 1: case 6:
 424                                                 return $this->msg( $tag, $val );
 425                                 }
 426
 427                         case 'PhotometricInterpretation':
 428                                 switch ($val) {
 429                                         case 2: case 6:
 430                                                 return $this->msg( $tag, $val );
 431                                 }
 432
 433                         case 'Orientation':
 434                                 switch ($val) {
 435                                         case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8:
 436                                                 return $this->msg( $tag, $val );
 437                                 }
 438
 439                         // TODO: If this field does not exist use 1
 440                         case 'PlanarConfiguration':
 441                                 switch ($val) {
 442                                         case 1: case 2:
 443                                                 return $this->msg( $tag, $val );
 444                                 }
 445
 446                         // TODO: YCbCrSubSampling
 447                         // TODO: YCbCrPositioning
 448                         // TODO: If this field does not exists use 2
 449                         case 'ResolutionUnit': #p26
 450                                 switch ($val) {
 451                                         case 2: case 3:
 452                                                 return $this->msg( $tag, $val );
 453                                 }
 454
 455                         // TODO: YCbCrCoefficients  #p27 (see annex E)
 456                         case 'ExifVersion': case 'FlashpixVersion':
 457                                 return "$val"/100;
 458
 459                         case 'ColorSpace':
 460                                 switch ($val) {
 461                                         case 1: case 'FFFF.H':
 462                                                 return $this->msg( $tag, $val );
 463                                 }
 464
 465                         case 'ComponentsConfiguration':
 466                                 switch ($val) {
 467                                         case 0: case 1: case 2: case 3: case 4: case 5: case 6:
 468                                                 return $this->msg( $tag, $val );
 469                                 }
 470
 471                         case 'DateTimeOriginal':
 472                         case 'DateTimeDigitized':
 473                                 return $wgLang->timeanddate( wfTimestamp(TS_MW, $val) );
 474                         case 'ExposureProgram':
 475                                 switch ($val) {
 476                                         case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8:
 477                                                 return $this->msg( $tag, $val );
 478                                 }
 479                         case 'MeteringMode':
 480                                 switch ($val) {
 481                                         case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 255:
 482                                                 return $this->msg( $tag, $val );
 483                                 }
 484                         case 'LightSource':
 485                                 switch ($val) {
 486                                         case 0: case 1: case 2: case 3: case 4: case 9: case 10: case 11:
 487                                         case 12: case 13: case 14: case 15: case 17: case 18: case 19: case 20:
 488                                         case 21: case 22: case 23: case 24: case 255:
 489                                                 return $this->msg( $tag, $val );
 490                                 }
 491                         // TODO: Flash
 492                         case 'SensingMethod':
 493                                 switch ($val) {
 494                                         case 1: case 2: case 3: case 4: case 5: case 7: case 8:
 495                                                 return $this->msg( $tag, $val );
 496                                 }
 497                         case 'FileSource':
 498                                 switch ($val) {
 499                                         case 3:
 500                                                 return $this->msg( $tag, $val );
 501                                 }
 502                         case 'SceneType':
 503                                 switch ($val) {
 504                                         case 1:
 505                                                 return $this->msg( $tag, $val );
 506                                 }
 507                         case 'CustomRendered':
 508                                 switch ($val) {
 509                                         case 0: case 1:
 510                                                 return $this->msg( $tag, $val );
 511                                 }
 512                         case 'ExposureMode':
 513                                 switch ($val) {
 514                                         case 0: case 1: case 2:
 515                                                 return $this->msg( $tag, $val );
 516                                 }
 517                         case 'WhiteBalance':
 518                                 switch ($val) {
 519                                         case 0: case 1:
 520                                                 return $this->msg( $tag, $val );
 521                                 }
 522                         case 'SceneCaptureType':
 523                                 switch ($val) {
 524                                         case 0: case 1: case 2: case 3:
 525                                                 return $this->msg( $tag, $val );
 526                                 }
 527                         case 'GainControl':
 528                                 switch ($val) {
 529                                         case 0: case 1: case 2: case 3: case 4:
 530                                                 return $this->msg( $tag, $val );
 531                                 }
 532                         case 'Contrast':
 533                                 switch ($val) {
 534                                         case 0: case 1: case 2:
 535                                                 return $this->msg( $tag, $val );
 536                                 }
 537                         case 'Saturation':
 538                                 switch ($val) {
 539                                         case 0: case 1: case 2:
 540                                                 return $this->msg( $tag, $val );
 541                                 }
 542                         case 'Sharpness':
 543                                 switch ($val) {
 544                                         case 0: case 1: case 2:
 545                                                 return $this->msg( $tag, $val );
 546                                 }
 547                         case 'SubjectDistanceRange':
 548                                 switch ($val) {
 549                                         case 0: case 1: case 2: case 3:
 550                                                 return $this->msg( $tag, $val );
 551                                 }
 552                         case 'GPSLatitudeRef':
 553                                 switch ($val) {
 554                                         case 'N': case 'S':
 555                                                 return $this->msg( $tag, $val );
 556                                 }
 557                         case 'GPSLongitudeRef':
 558                                 switch ($val) {
 559                                         case 'E': case 'W':
 560                                                 return $this->msg( $tag, $val );
 561                                 }
 562                         case 'GPSStatus':
 563                                 switch ($val) {
 564                                         case 'A': case 'V':
 565                                                 return $this->msg( $tag, $val );
 566                                 }
 567                         case 'GPSMeasureMode':
 568                                 switch ($val) {
 569                                         case 2: case 3:
 570                                                 return $this->msg( $tag, $val );
 571                                 }
 572                         case 'GPSSpeedRef':
 573                                 switch ($val) {
 574                                         case 'K': case 'M': case 'N':
 575                                                 return $this->msg( $tag, $val );
 576                                 }
 577                         case 'GPSTrackRef':
 578                                 switch ($val) {
 579                                         case 'T': case 'M':
 580                                                 return $this->msg( $tag, $val );
 581                                 }
 582                         case 'GPSImgDirectionRef':
 583                                 switch ($val) {
 584                                         case 'T': case 'M':
 585                                                 return $this->msg( $tag, $val );
 586                                 }
 587                         case 'GPSDestLatitudeRef':
 588                                 switch ($val) {
 589                                         case 'N': case 'S':
 590                                                 return $this->msg( $tag, $val );
 591                                 }
 592                         case 'GPSDestLongitudeRef':
 593                                 switch ($val) {
 594                                         case 'E': case 'W':
 595                                                 return $this->msg( $tag, $val );
 596                                 }
 597                         case 'GPSDestBearingRef':
 598                                 switch ($val) {
 599                                         case 'T': case 'M':
 600                                                 return $this->msg( $tag, $val );
 601                                 }
 602                         case 'GPSDateStamp':
 603                                 return $wgLang->date( substr($val, 0, 4) . substr($val, 5, 2) . substr($val, 8, 2) . 000000 );
 604
 605                         // This is not in the Exif standard, just a special
 606                         // case for our purposes which enables wikis to wikify
 607                         // the make and model to write articles about them.
 608                         case 'Make': case 'Model':
 609                                 return wfMsg( strtolower( "exif-$tag-value" ), $val );
 610                         default:
 611                                 return $val;
 612                 }
 613         }
 614
 615         /**
 616          * Conviniance function for format()
 617          *
 618          * @param string $tag The tag name to pass on
 619          * @param string $val The value of the tag
 620          * @return string A wfMsg of "exif-$tag-$val" in lower case
 621          */
 622         function msg( $tag, $val ) {
 623                 return wfMsg( strtolower("exif-$tag-$val") );
 624         }
 625 }
 626 } // MEDIAWIKI