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  * Exif tag type definition
  32  */
  33 define('MW_EXIF_BYTE', 1);              # An 8-bit unsigned integer.
  34 define('MW_EXIF_ASCII', 2);             # An 8-bit byte containing one 7-bit ASCII code. The final byte is terminated with NULL.
  35 define('MW_EXIF_SHORT', 3);             # A 16-bit (2-byte) unsigned integer.
  36 define('MW_EXIF_LONG', 4);              # A 32-bit (4-byte) unsigned integer.
  37 define('MW_EXIF_RATIONAL', 5);          # Two LONGs. The first LONG is the numerator and the second LONG expresses the denominator
  38 define('MW_EXIF_UNDEFINED', 7);         # An 8-bit byte that can take any value depending on the field definition
  39 define('MW_EXIF_SLONG', 9);             # A 32-bit (4-byte) signed integer (2's complement notation),
  40 define('MW_EXIF_SRATIONAL', 10);        # Two SLONGs. The first SLONG is the numerator and the second SLONG is the denominator.
  41 /**#@-*/
  42
  43
  44 /**
  45  * @package MediaWiki
  46  * @subpackage Metadata
  47  */
  48 class Exif {
  49         /**#@+
  50          * @var array
  51          */
  52
  53         /**
  54          * Exif tags grouped by category, the tagname itself is the key and the type
  55          * is the value, in the case of more than one possible value type they are
  56          * seperated by commas.
  57          *
  58          * @access private
  59          */
  60         var $mExif;
  61
  62         /**
  63          * A one dimentional array of all Exif tags
  64          */
  65         var $mFlatExif;
  66
  67         /**
  68          * A one dimentional array of all Exif tags that we'd want to save in
  69          * the database or present on a page.
  70          */
  71         var $mValidExif;
  72
  73         /**#@-*/
  74
  75         /**
  76          * Constructor
  77          */
  78         function Exif() {
  79                 /**
  80                  * Page numbers here refer to pages in the EXIF 2.2 standard
  81                  *
  82                  * @link http://exif.org/Exif2-2.PDF The Exif 2.2 specification
  83                  */
  84                 $this->mExif = array(
  85                         # TIFF Rev. 6.0 Attribute Information (p22)
  86                         'tiff' => array(
  87                                 # Tags relating to image structure
  88                                 'structure' => array(
  89                                         'ImageWidth' => MW_EXIF_SHORT.','.MW_EXIF_LONG,         # Image width
  90                                         'ImageLength' => MW_EXIF_SHORT.','.MW_EXIF_LONG,        # Image height
  91                                         'BitsPerSample' => MW_EXIF_SHORT,               # Number of bits per component
  92                                         # "When a primary image is JPEG compressed, this designation is not"
  93                                         # "necessary and is omitted." (p23)
  94                                         'Compression' => MW_EXIF_SHORT,                 # Compression scheme #p23
  95                                         'PhotometricInterpretation' => MW_EXIF_SHORT,   # Pixel composition #p23
  96                                         'Orientation' => MW_EXIF_SHORT,                 # Orientation of image #p24
  97                                         'SamplesPerPixel' => MW_EXIF_SHORT,             # Number of components
  98                                         'PlanarConfiguration' => MW_EXIF_SHORT,         # Image data arrangement #p24
  99                                         'YCbCrSubSampling' => MW_EXIF_SHORT,            # Subsampling ratio of Y to C #p24
 100                                         'YCbCrPositioning' => MW_EXIF_SHORT,            # Y and C positioning #p24-25
 101                                         'XResolution' => MW_EXIF_RATIONAL,              # Image resolution in width direction
 102                                         'YResolution' => MW_EXIF_RATIONAL,              # Image resolution in height direction
 103                                         'ResolutionUnit' => MW_EXIF_SHORT,              # Unit of X and Y resolution #(p26)
 104                                 ),
 105
 106                                 # Tags relating to recording offset
 107                                 'offset' => array(
 108                                         'StripOffsets' => MW_EXIF_SHORT.','.MW_EXIF_LONG,                       # Image data location
 109                                         'RowsPerStrip' => MW_EXIF_SHORT.','.MW_EXIF_LONG,                       # Number of rows per strip
 110                                         'StripByteCounts' => MW_EXIF_SHORT.','.MW_EXIF_LONG,                    # Bytes per compressed strip
 111                                         'JPEGInterchangeFormat' => MW_EXIF_SHORT.','.MW_EXIF_LONG,              # Offset to JPEG SOI
 112                                         'JPEGInterchangeFormatLength' => MW_EXIF_SHORT.','.MW_EXIF_LONG,        # Bytes of JPEG data
 113                                 ),
 114
 115                                 # Tags relating to image data characteristics
 116                                 'characteristics' => array(
 117                                         'TransferFunction' => MW_EXIF_SHORT,            # Transfer function
 118                                         'WhitePoint' => MW_EXIF_RATIONAL,               # White point chromaticity
 119                                         'PrimaryChromaticities' => MW_EXIF_RATIONAL,    # Chromaticities of primarities
 120                                         'YCbCrCoefficients' => MW_EXIF_RATIONAL,        # Color space transformation matrix coefficients #p27
 121                                         'ReferenceBlackWhite' => MW_EXIF_RATIONAL       # Pair of black and white reference values
 122                                 ),
 123
 124                                 # Other tags
 125                                 'other' => array(
 126                                         'DateTime' => MW_EXIF_ASCII,            # File change date and time
 127                                         'ImageDescription' => MW_EXIF_ASCII,    # Image title
 128                                         'Make' => MW_EXIF_ASCII,                # Image input equipment manufacturer
 129                                         'Model' => MW_EXIF_ASCII,               # Image input equipment model
 130                                         'Software' => MW_EXIF_ASCII,            # Software used
 131                                         'Artist' => MW_EXIF_ASCII,              # Person who created the image
 132                                         'Copyright' => MW_EXIF_ASCII,           # Copyright holder
 133                                 ),
 134                         ),
 135
 136                         # Exif IFD Attribute Information (p30-31)
 137                         'exif' => array(
 138                                 # Tags relating to version
 139                                 'version' => array(
 140                                         # TODO: NOTE: Nonexistence of this field is taken to mean nonconformance
 141                                         # to the EXIF 2.1 AND 2.2 standards
 142                                         'ExifVersion' => MW_EXIF_UNDEFINED,     # Exif version
 143                                         'FlashpixVersion' => MW_EXIF_UNDEFINED, # Supported Flashpix version #p32
 144                                 ),
 145
 146                                 # Tags relating to Image Data Characteristics
 147                                 'characteristics' => array(
 148                                         'ColorSpace' => MW_EXIF_SHORT,          # Color space information #p32
 149                                 ),
 150
 151                                 # Tags relating to image configuration
 152                                 'configuration' => array(
 153                                         'ComponentsConfiguration' => MW_EXIF_UNDEFINED,         # Meaning of each component #p33
 154                                         'CompressedBitsPerPixel' => MW_EXIF_RATIONAL,           # Image compression mode
 155                                         'PixelYDimension' => MW_EXIF_SHORT.','.MW_EXIF_LONG,            # Valid image width
 156                                         'PixelXDimension' => MW_EXIF_SHORT.','.MW_EXIF_LONG,            # Valind image height
 157                                 ),
 158
 159                                 # Tags relating to related user information
 160                                 'user' => array(
 161                                         'MakerNote' => MW_EXIF_UNDEFINED,                       # Manufacturer notes
 162                                         'UserComment' => MW_EXIF_UNDEFINED,                     # User comments #p34
 163                                 ),
 164
 165                                 # Tags relating to related file information
 166                                 'related' => array(
 167                                         'RelatedSoundFile' => MW_EXIF_ASCII,                    # Related audio file
 168                                 ),
 169
 170                                 # Tags relating to date and time
 171                                 'dateandtime' => array(
 172                                         'DateTimeOriginal' => MW_EXIF_ASCII,                    # Date and time of original data generation #p36
 173                                         'DateTimeDigitized' => MW_EXIF_ASCII,                   # Date and time of original data generation
 174                                         'SubSecTime' => MW_EXIF_ASCII,                          # DateTime subseconds
 175                                         'SubSecTimeOriginal' => MW_EXIF_ASCII,                  # DateTimeOriginal subseconds
 176                                         'SubSecTimeDigitized' => MW_EXIF_ASCII,                 # DateTimeDigitized subseconds
 177                                 ),
 178
 179                                 # Tags relating to picture-taking conditions (p31)
 180                                 'conditions' => array(
 181                                         'ExposureTime' => MW_EXIF_RATIONAL,                     # Exposure time
 182                                         'FNumber' => MW_EXIF_RATIONAL,                          # F Number
 183                                         'ExposureProgram' => MW_EXIF_SHORT,                     # Exposure Program #p38
 184                                         'SpectralSensitivity' => MW_EXIF_ASCII,                 # Spectral sensitivity
 185                                         'ISOSpeedRatings' => MW_EXIF_SHORT,                     # ISO speed rating
 186                                         'OECF' => MW_EXIF_UNDEFINED,                            # Optoelectronic conversion factor
 187                                         'ShutterSpeedValue' => MW_EXIF_SRATIONAL,               # Shutter speed
 188                                         'ApertureValue' => MW_EXIF_RATIONAL,                    # Aperture
 189                                         'BrightnessValue' => MW_EXIF_SRATIONAL,                 # Brightness
 190                                         'ExposureBiasValue' => MW_EXIF_SRATIONAL,               # Exposure bias
 191                                         'MaxApertureValue' => MW_EXIF_RATIONAL,                 # Maximum land aperture
 192                                         'SubjectDistance' => MW_EXIF_RATIONAL,                  # Subject distance
 193                                         'MeteringMode' => MW_EXIF_SHORT,                        # Metering mode #p40
 194                                         'LightSource' => MW_EXIF_SHORT,                         # Light source #p40-41
 195                                         'Flash' => MW_EXIF_SHORT,                               # Flash #p41-42
 196                                         'FocalLength' => MW_EXIF_RATIONAL,                      # Lens focal length
 197                                         'SubjectArea' => MW_EXIF_SHORT,                         # Subject area
 198                                         'FlashEnergy' => MW_EXIF_RATIONAL,                      # Flash energy
 199                                         'SpatialFrequencyResponse' => MW_EXIF_UNDEFINED,        # Spatial frequency response
 200                                         'FocalPlaneXResolution' => MW_EXIF_RATIONAL,            # Focal plane X resolution
 201                                         'FocalPlaneYResolution' => MW_EXIF_RATIONAL,            # Focal plane Y resolution
 202                                         'FocalPlaneResolutionUnit' => MW_EXIF_SHORT,            # Focal plane resolution unit
 203                                         'SubjectLocation' => MW_EXIF_SHORT,                     # Subject location
 204                                         'ExposureIndex' => MW_EXIF_RATIONAL,                    # Exposure index
 205                                         'SensingMethod' => MW_EXIF_SHORT,                       # Sensing method #p46
 206                                         'FileSource' => MW_EXIF_UNDEFINED,                      # File source #p47
 207                                         'SceneType' => MW_EXIF_UNDEFINED,                       # Scene type #p47
 208                                         'CFAPattern' => MW_EXIF_UNDEFINED,                      # CFA pattern
 209                                         'CustomRendered' => MW_EXIF_SHORT,                      # Custom image processing #p48
 210                                         'ExposureMode' => MW_EXIF_SHORT,                        # Exposure mode #p48
 211                                         'WhiteBalance' => MW_EXIF_SHORT,                        # White Balance #p49
 212                                         'DigitalZoomRatio' => MW_EXIF_RATIONAL,                 # Digital zoom ration
 213                                         'FocalLengthIn35mmFilm' => MW_EXIF_SHORT,               # Focal length in 35 mm film
 214                                         'SceneCaptureType' => MW_EXIF_SHORT,                    # Scene capture type #p49
 215                                         'GainControl' => MW_EXIF_RATIONAL,                      # Scene control #p49-50
 216                                         'Contrast' => MW_EXIF_SHORT,                            # Contrast #p50
 217                                         'Saturation' => MW_EXIF_SHORT,                          # Saturation #p50
 218                                         'Sharpness' => MW_EXIF_SHORT,                           # Sharpness #p50
 219                                         'DeviceSettingDescription' => MW_EXIF_UNDEFINED,        # Desice settings description
 220                                         'SubjectDistanceRange' => MW_EXIF_SHORT,                # Subject distance range #p51
 221                                 ),
 222
 223                                 'other' => array(
 224                                         'ImageUniqueID' => MW_EXIF_ASCII,       # Unique image ID
 225                                 ),
 226                         ),
 227
 228                         # GPS Attribute Information (p52)
 229                         'gps' => array(
 230                                 'GPSVersionID' => MW_EXIF_BYTE,                 # GPS tag version
 231                                 'GPSLatitudeRef' => MW_EXIF_ASCII,              # North or South Latitude #p52-53
 232                                 'GPSLatitude' => MW_EXIF_RATIONAL,              # Latitude
 233                                 'GPSLongitudeRef' => MW_EXIF_ASCII,             # East or West Longitude #p53
 234                                 'GPSLongitude' => MW_EXIF_RATIONAL,             # Longitude
 235                                 'GPSAltitudeRef' => MW_EXIF_BYTE,               # Altitude reference
 236                                 'GPSAltitude' => MW_EXIF_RATIONAL,              # Altitude
 237                                 'GPSTimeStamp' => MW_EXIF_RATIONAL,             # GPS time (atomic clock)
 238                                 'GPSSatellites' => MW_EXIF_ASCII,               # Satellites used for measurement
 239                                 'GPSStatus' => MW_EXIF_ASCII,                   # Receiver status #p54
 240                                 'GPSMeasureMode' => MW_EXIF_ASCII,              # Measurement mode #p54-55
 241                                 'GPSDOP' => MW_EXIF_RATIONAL,                   # Measurement precision
 242                                 'GPSSpeedRef' => MW_EXIF_ASCII,                 # Speed unit #p55
 243                                 'GPSSpeed' => MW_EXIF_RATIONAL,                 # Speed of GPS receiver
 244                                 'GPSTrackRef' => MW_EXIF_ASCII,                 # Reference for direction of movement #p55
 245                                 'GPSTrack' => MW_EXIF_RATIONAL,                 # Direction of movement
 246                                 'GPSImgDirectionRef' => MW_EXIF_ASCII,          # Reference for direction of image #p56
 247                                 'GPSImgDirection' => MW_EXIF_RATIONAL,          # Direction of image
 248                                 'GPSMapDatum' => MW_EXIF_ASCII,                 # Geodetic survey data used
 249                                 'GPSDestLatitudeRef' => MW_EXIF_ASCII,          # Reference for latitude of destination #p56
 250                                 'GPSDestLatitude' => MW_EXIF_RATIONAL,          # Latitude destination
 251                                 'GPSDestLongitudeRef' => MW_EXIF_ASCII,         # Reference for longitude of destination #p57
 252                                 'GPSDestLongitude' => MW_EXIF_RATIONAL,         # Longitude of destination
 253                                 'GPSDestBearingRef' => MW_EXIF_ASCII,           # Reference for bearing of destination #p57
 254                                 'GPSDestBearing' => MW_EXIF_RATIONAL,           # Bearing of destination
 255                                 'GPSDestDistanceRef' => MW_EXIF_ASCII,          # Reference for distance to destination #p57-58
 256                                 'GPSDestDistance' => MW_EXIF_RATIONAL,          # Distance to destination
 257                                 'GPSProcessingMethod' => MW_EXIF_UNDEFINED,     # Name of GPS processing method
 258                                 'GPSAreaInformation' => MW_EXIF_UNDEFINED,      # Name of GPS area
 259                                 'GPSDateStamp' => MW_EXIF_ASCII,                # GPS date
 260                                 'GPSDifferential' => MW_EXIF_SHORT,             # GPS differential correction
 261                         ),
 262                 );
 263
 264                 $this->makeFlatExifTags();
 265                 $this->makeValidExifTags();
 266         }
 267
 268         /**
 269          * Get the raw list of exiftags
 270          *
 271          * @access private
 272          * @return array
 273         */
 274         function getExif() {
 275                 return $this->mExif;
 276         }
 277
 278         /**
 279          * Generate a flat list of the exif tags
 280          */
 281         function makeFlatExifTags() {
 282                 $exif = $this->getExif();
 283                 $this->extractTags( $exif );
 284         }
 285
 286         /**
 287          * A recursing extractor function used by makeFlatExifTags()
 288          *
 289          * Note: This used to use an array_walk function, but it made PHP5
 290          * segfault, see `cvs diff -u -r 1.4 -r 1.5 Exif.php`
 291          */
 292         function extractTags( $tagset ) {
 293                 foreach( $tagset as $key => $val ) {
 294                         if( is_array( $val ) ) {
 295                                 $this->extractTags( $val );
 296                         } else {
 297                                 $this->mFlatExif[$key] = $val;
 298                         }
 299                 }
 300         }
 301
 302         /**
 303          * Produce a list of all Exif tags appropriate for user output
 304          *
 305          * Produce a list of all tags that we want to show in output, in order not to
 306          * output binary gibberish such as raw thumbnails we strip all tags
 307          * with the datatype of UNDEFINED.
 308          *
 309          * @todo We might actually want to display some of the UNDEFINED
 310          *       stuff, but we strip it for now.
 311          */
 312         function makeValidExifTags() {
 313                 foreach( $this->mFlatExif as $key => $val ) {
 314                         if( strpos( $val, (string)MW_EXIF_UNDEFINED ) !== false ) {
 315                                 continue;
 316                         }
 317                         $this->mValidExif[] = $key;
 318                 }
 319         }
 320
 321          /**
 322           * The version of the output format
 323           *
 324           * Before the actual metadata information is saved in the database we
 325           * strip some of it since we don't want to save things like thumbnails
 326           * which usually accompany Exif data. This value gets saved in the
 327           * database along with the actual Exif data, and if the version in the
 328           * database doesn't equal the value returned by this function the Exif
 329           * data is regenerated.
 330           *
 331           * @return int
 332           */
 333         function version() {
 334                 return 1; // We don't need no bloddy constants!
 335         }
 336
 337         /**#@+
 338          * Validates if a tag value is of the type it should be according to the Exif spec
 339          *
 340          * @param mixed $in The input value to check
 341          * @return bool
 342          */
 343         function isByte( $in ) {
 344                 $fname = 'isByte';
 345                 if ( is_numeric( $in ) && $in >= 0 && $in <= 255 ) {
 346                         wfDebug("Exif::$fname: accepted: '$in' (type: " . gettype( $in ) . ")\n");
 347                         return true;
 348                 } else {
 349                         wfDebug("Exif::$fname: rejected: '$in' (type: " . gettype( $in ) . ")\n");
 350                         return false;
 351                 }
 352         }
 353
 354         function isASCII( $in ) {
 355                 wfDebug("Exif::isASCII: input was '$in'\n");
 356                 return true; // TODO: FIXME
 357         }
 358
 359         function isShort( $in ) {
 360                 $fname = 'isShort';
 361                 if ( is_numeric( $in ) && $in >= 0 && $in <= 65536 ) {
 362                         wfDebug("Exif::$fname: accepted: '$in' (type: " . gettype( $in ) . ")\n");
 363                         return true;
 364                 } else {
 365                         wfDebug("Exif::$fname: rejected: '$in' (type: " . gettype( $in ) . ")\n");
 366                         return false;
 367                 }
 368         }
 369
 370         function isLong( $in ) {
 371                 $fname = 'isLong';
 372                 if ( is_numeric( $in ) && $in >= 0 && $in <= 4294967296 ) {
 373                         wfDebug("Exif::$fname: accepted: '$in' (type: " . gettype( $in ) . ")\n");
 374                         return true;
 375                 } else {
 376                         wfDebug("Exif::$fname: rejected: '$in' (type: " . gettype( $in ) . ")\n");
 377                         return false;
 378                 }
 379         }
 380
 381         function isRational( $in ) {
 382                 $fname = 'isRational';
 383                 $a = explode( '/', $in, 2 );
 384                 if ( $this->isLong( $a[0] ) && $this->isLong( $a[1] ) ) {
 385                         wfDebug("Exif::$fname: accepted: '$in' (type: " . gettype( $in ) . ")\n");
 386                         return true;
 387                 } else {
 388                         wfDebug("Exif::$fname: rejected: '$in' (type: " . gettype( $in ) . ")\n");
 389                         return false;
 390                 }
 391         }
 392
 393         function isUndefined( $in ) {
 394                 $fname = 'isUndefined';
 395                 wfDebug("Exif::$fname: input was '$in'\n");
 396                 return true;
 397         }
 398
 399         function isSlong( $in ) {
 400                 $fname = 'isSlong';
 401                 if ( $this->isLong( abs( $in ) ) ) {
 402                         wfDebug("Exif::$fname: accepted: '$in' (type: " . gettype( $in ) . ")\n");
 403                         return true;
 404                 } else {
 405                         wfDebug("Exif::$fname: rejected: '$in' (type: " . gettype( $in ) . ")\n");
 406                         return false;
 407                 }
 408         }
 409
 410         function isSrational( $in ) {
 411                 $fname = 'isSrational';
 412                 $a = explode( '/', $in, 2 );
 413                 if ( $this->isSlong( $a[0] ) && $this->isSlong( $a[1] ) ) {
 414                          wfDebug("Exif::$fname: accepted: '$in' (type: " . gettype( $in ) . ")\n");
 415                          return true;
 416                 } else {
 417                         wfDebug("Exif::$fname: rejected: '$in' (type: " . gettype( $in ) . ")\n");
 418                         return false;
 419                 }
 420         }
 421         /**#@-*/
 422
 423         /**
 424          * Validates if a tag has a legal value according to the Exif spec, presumes
 425          * that the given tag is valid ( has been checked in advance with
 426          * $this->mValidExif )
 427          *
 428          * @param string $tag The tag to check
 429          * @param mixed  $val The value of the tag
 430          * @return bool
 431          */
 432         function validate( $tag, $val ) {
 433                 // Fucks up if not typecast
 434                 switch( (string)$this->mFlatExif[$tag] ) {
 435                         case (string)MW_EXIF_BYTE:
 436                                 return $this->isByte( $val );
 437                         case (string)MW_EXIF_ASCII:
 438                                 return $this->isASCII( $val );
 439                         case (string)MW_EXIF_SHORT:
 440                                 return $this->isShort( $val );
 441                         case (string)MW_EXIF_LONG:
 442                                 return $this->isLong( $val );
 443                         case (string)MW_EXIF_RATIONAL:
 444                                 return $this->isRational( $val );
 445                         case (string)MW_EXIF_UNDEFINED:
 446                                 return $this->isUndefined( $val );
 447                         case (string)MW_EXIF_SLONG:
 448                                 return $this->isSlong( $val );
 449                         case (string)MW_EXIF_SRATIONAL:
 450                                 return $this->isSrational( $val );
 451                         case (string)MW_EXIF_SHORT.','.MW_EXIF_LONG:
 452                                 return $this->isShort( $val ) || $this->isLong( $val );
 453                         default:
 454                                 wfDebug( "Exif::validate: The tag \"$tag\" had an invalid value: \"$val\"\n" );
 455                                 return false;
 456                 }
 457         }
 458
 459         /**
 460          * Numbers given by Exif user agents are often magical, that is they
 461          * should be replaced by a detailed explanation depending on their
 462          * value which most of the time are plain integers. This function
 463          * formats Exif values into human readable form.
 464          *
 465          * @param string $tag The tag to be formatted
 466          * @param mixed  $val The value of the tag
 467          * @return string
 468          */
 469         function format( $tag, $val ) {
 470                 global $wgLang;
 471
 472                 switch( $tag ) {
 473                 case 'Compression':
 474                         switch( $val ) {
 475                         case 1: case 6:
 476                                 return $this->msg( $tag, $val );
 477                         }
 478                         break;
 479
 480                 case 'PhotometricInterpretation':
 481                         switch( $val ) {
 482                         case 2: case 6:
 483                                 return $this->msg( $tag, $val );
 484                         }
 485                         break;
 486
 487                 case 'Orientation':
 488                         switch( $val ) {
 489                         case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8:
 490                                 return $this->msg( $tag, $val );
 491                         }
 492                         break;
 493
 494                 case 'PlanarConfiguration':
 495                         switch( $val ) {
 496                         case 1: case 2:
 497                                 return $this->msg( $tag, $val );
 498                         }
 499                         break;
 500
 501                 // TODO: YCbCrSubSampling
 502                 // TODO: YCbCrPositioning
 503                 // TODO: If this field does not exists use 2
 504                 case 'ResolutionUnit': #p26
 505                         switch( $val ) {
 506                         case 2: case 3:
 507                                 return $this->msg( $tag, $val );
 508                         }
 509                         break;
 510
 511                 // TODO: YCbCrCoefficients  #p27 (see annex E)
 512                 case 'ExifVersion': case 'FlashpixVersion':
 513                         return "$val"/100;
 514
 515                 case 'ColorSpace':
 516                         switch( $val ) {
 517                         case 1: case 'FFFF.H':
 518                                 return $this->msg( $tag, $val );
 519                         }
 520                         break;
 521
 522                 case 'ComponentsConfiguration':
 523                         switch( $val ) {
 524                         case 0: case 1: case 2: case 3: case 4: case 5: case 6:
 525                                 return $this->msg( $tag, $val );
 526                         }
 527                         break;
 528
 529                 case 'DateTime':
 530                 case 'DateTimeOriginal':
 531                 case 'DateTimeDigitized':
 532                         return $wgLang->timeanddate( wfTimestamp(TS_MW, $val) );
 533
 534                 case 'ExposureProgram':
 535                         switch( $val ) {
 536                         case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8:
 537                                 return $this->msg( $tag, $val );
 538                         }
 539                         break;
 540
 541                 case 'MeteringMode':
 542                         switch( $val ) {
 543                         case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 255:
 544                                 return $this->msg( $tag, $val );
 545                         }
 546                         break;
 547
 548                 case 'LightSource':
 549                         switch( $val ) {
 550                         case 0: case 1: case 2: case 3: case 4: case 9: case 10: case 11:
 551                         case 12: case 13: case 14: case 15: case 17: case 18: case 19: case 20:
 552                         case 21: case 22: case 23: case 24: case 255:
 553                                 return $this->msg( $tag, $val );
 554                         }
 555                         break;
 556
 557                 // TODO: Flash
 558                 case 'SensingMethod':
 559                         switch( $val ) {
 560                         case 1: case 2: case 3: case 4: case 5: case 7: case 8:
 561                                 return $this->msg( $tag, $val );
 562                         }
 563                         break;
 564
 565                 case 'FileSource':
 566                         switch( $val ) {
 567                         case 3:
 568                                 return $this->msg( $tag, $val );
 569                         }
 570                         break;
 571
 572                 case 'SceneType':
 573                         switch( $val ) {
 574                         case 1:
 575                                 return $this->msg( $tag, $val );
 576                         }
 577                         break;
 578
 579                 case 'CustomRendered':
 580                         switch( $val ) {
 581                         case 0: case 1:
 582                                 return $this->msg( $tag, $val );
 583                         }
 584                         break;
 585
 586                 case 'ExposureMode':
 587                         switch( $val ) {
 588                         case 0: case 1: case 2:
 589                                 return $this->msg( $tag, $val );
 590                         }
 591                         break;
 592
 593                 case 'WhiteBalance':
 594                         switch( $val ) {
 595                         case 0: case 1:
 596                                 return $this->msg( $tag, $val );
 597                         }
 598                         break;
 599
 600                 case 'SceneCaptureType':
 601                         switch( $val ) {
 602                         case 0: case 1: case 2: case 3:
 603                                 return $this->msg( $tag, $val );
 604                         }
 605                         break;
 606
 607                 case 'GainControl':
 608                         switch( $val ) {
 609                         case 0: case 1: case 2: case 3: case 4:
 610                                 return $this->msg( $tag, $val );
 611                         }
 612                         break;
 613
 614                 case 'Contrast':
 615                         switch( $val ) {
 616                         case 0: case 1: case 2:
 617                                 return $this->msg( $tag, $val );
 618                         }
 619                         break;
 620
 621                 case 'Saturation':
 622                         switch( $val ) {
 623                         case 0: case 1: case 2:
 624                                 return $this->msg( $tag, $val );
 625                         }
 626                         break;
 627
 628                 case 'Sharpness':
 629                         switch( $val ) {
 630                         case 0: case 1: case 2:
 631                                 return $this->msg( $tag, $val );
 632                         }
 633                         break;
 634
 635                 case 'SubjectDistanceRange':
 636                         switch( $val ) {
 637                         case 0: case 1: case 2: case 3:
 638                                 return $this->msg( $tag, $val );
 639                         }
 640                         break;
 641
 642                 case 'GPSLatitudeRef':
 643                         switch( $val ) {
 644                         case 'N': case 'S':
 645                                 return $this->msg( $tag, $val );
 646                         }
 647                         break;
 648
 649                 case 'GPSLongitudeRef':
 650                         switch( $val ) {
 651                         case 'E': case 'W':
 652                                 return $this->msg( $tag, $val );
 653                         }
 654                         break;
 655
 656                 case 'GPSStatus':
 657                         switch( $val ) {
 658                         case 'A': case 'V':
 659                                 return $this->msg( $tag, $val );
 660                         }
 661                         break;
 662
 663                 case 'GPSMeasureMode':
 664                         switch( $val ) {
 665                         case 2: case 3:
 666                                 return $this->msg( $tag, $val );
 667                         }
 668                         break;
 669
 670                 case 'GPSSpeedRef':
 671                         switch( $val ) {
 672                         case 'K': case 'M': case 'N':
 673                                 return $this->msg( $tag, $val );
 674                         }
 675                         break;
 676
 677                 case 'GPSTrackRef':
 678                         switch( $val ) {
 679                         case 'T': case 'M':
 680                                 return $this->msg( $tag, $val );
 681                         }
 682                         break;
 683
 684                 case 'GPSImgDirectionRef':
 685                         switch( $val ) {
 686                         case 'T': case 'M':
 687                                 return $this->msg( $tag, $val );
 688                         }
 689                         break;
 690
 691                 case 'GPSDestLatitudeRef':
 692                         switch( $val ) {
 693                         case 'N': case 'S':
 694                                 return $this->msg( $tag, $val );
 695                         }
 696                         break;
 697
 698                 case 'GPSDestLongitudeRef':
 699                         switch( $val ) {
 700                         case 'E': case 'W':
 701                                 return $this->msg( $tag, $val );
 702                         }
 703                         break;
 704
 705                 case 'GPSDestBearingRef':
 706                         switch( $val ) {
 707                         case 'T': case 'M':
 708                                 return $this->msg( $tag, $val );
 709                         }
 710                         break;
 711                 case 'GPSDateStamp':
 712                         return $wgLang->date( substr( $val, 0, 4 ) . substr( $val, 5, 2 ) . substr( $val, 8, 2 ) . '000000' );
 713
 714                 // This is not in the Exif standard, just a special
 715                 // case for our purposes which enables wikis to wikify
 716                 // the make, model and software name to link to their articles.
 717                 case 'Make':
 718                 case 'Model':
 719                 case 'Software':
 720                         return wfMsg( strtolower( "exif-$tag-value" ), $val );
 721                 default:
 722                         return $val;
 723                 }
 724         }
 725
 726         /**
 727          * Conviniance function for format()
 728          *
 729          * @param string $tag The tag name to pass on
 730          * @param string $val The value of the tag
 731          * @return string A wfMsg of "exif-$tag-$val" in lower case
 732          */
 733         function msg( $tag, $val ) {
 734                 return wfMsg( strtolower("exif-$tag-$val") );
 735         }
 736 }
 737
 738 } // MEDIAWIKI