<?php

/*  PEL: PHP Exif Library.  A library with support for reading and
 *  writing all Exif headers in JPEG and TIFF images using PHP.
 *
 *  Copyright (C) 2004, 2005, 2006  Martin Geisler.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program in the file COPYING; if not, write to the
 *  Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
 *  Boston, MA 02110-1301 USA
 */

/* $Id: PelTag.php 472 2006-11-19 20:29:14Z mgeisler $ */


/**
 * Namespace for functions operating on Exif tags.
 *
 * @author Martin Geisler <mgeisler@users.sourceforge.net>
 * @version $Revision: 472 $
 * @date $Date: 2006-11-19 21:29:14 +0100 (Sun, 19 Nov 2006) $
 * @license http://www.gnu.org/licenses/gpl.html GNU General Public
 * License (GPL)
 * @package PEL
 */

/**#@+ Required class definitions. */
require_once('Pel.php');
require_once('PelIfd.php');
/**#@-*/


/**
 * Class with static methods for Exif tags.
 *
 * This class defines the constants that represents the Exif tags
 * known to PEL.  They are supposed to be used whenever one needs to
 * specify an Exif tag, and they will be denoted by the pseudo-type
 * {@link PelTag} throughout the documentation.
 *
 * Please note that the constrains on the format and number of
 * components given here are advisory only.  To follow the Exif
 * specification one should obey them, but there is nothing that
 * prevents you from creating an {@link IMAGE_LENGTH} entry with two
 * or more components, even though the standard says that there should
 * be exactly one component.
 *
 * All the methods in this class are static and should be called with
 * the Exif tag on which they should operate.
 *
 * @author Martin Geisler <mgeisler@users.sourceforge.net>
 * @package PEL
 */
class PelTag {

  /**
   * Interoperability index.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 4.
   */
  const INTEROPERABILITY_INDEX                            = 0x0001;

  /**
   * Interoperability version.
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: 4.
   */
  const INTEROPERABILITY_VERSION                          = 0x0002;

  /**
   * Image width.
   *
   * Format: {@link PelFormat::SHORT} or {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const IMAGE_WIDTH                                       = 0x0100;

  /**
   * Image length.
   *
   * Format: {@link PelFormat::SHORT} or {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const IMAGE_LENGTH                                      = 0x0101;

  /**
   * Number of bits per component.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 3.
   */
  const BITS_PER_SAMPLE                                   = 0x0102;

  /**
   * Compression scheme.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const COMPRESSION                                       = 0x0103;

  /**
   * Pixel composition.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const PHOTOMETRIC_INTERPRETATION                        = 0x0106;

  /**
   * Fill Orde
   *
   * Format: Unknown.
   *
   * Components: Unknown.
   */
  const FILL_ORDER                                        = 0x010A;

  /**
   * Document Name
   *
   * Format: Unknown.
   *
   * Components: Unknown.
   */
  const DOCUMENT_NAME                                     = 0x010D;

  /**
   * Image Description
   *
   * Format: {@link PelEntryAscii}.
   *
   * Components: any number.
   */
  const IMAGE_DESCRIPTION                                 = 0x010E;

  /**
   * Manufacturer
   *
   * Format: {@link PelEntryAscii}.
   *
   * Components: any number.
   */
  const MAKE                                              = 0x010F;

  /**
   * Model
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: any number.
   */
  const MODEL                                             = 0x0110;

  /**
   * Strip Offsets
   *
   * Format: {@link PelFormat::SHORT} or {@link PelFormat::LONG}.
   *
   * Components: any number.
   */
  const STRIP_OFFSETS                                     = 0x0111;

  /**
   * Orientation of image.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const ORIENTATION                                       = 0x0112;

  /**
   * Number of components.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const SAMPLES_PER_PIXEL                                 = 0x0115;

  /**
   * Rows per Strip
   *
   * Format: {@link PelFormat::SHORT} or {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const ROWS_PER_STRIP                                    = 0x0116;

  /**
   * Strip Byte Count
   *
   * Format: {@link PelFormat::SHORT} or {@link PelFormat::LONG}.
   *
   * Components: any number.
   */
  const STRIP_BYTE_COUNTS                                 = 0x0117;

  /**
   * Image resolution in width direction.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const X_RESOLUTION                                      = 0x011A;

  /**
   * Image resolution in height direction.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const Y_RESOLUTION                                      = 0x011B;

  /**
   * Image data arrangement.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const PLANAR_CONFIGURATION                              = 0x011C;

  /**
   * Unit of X and Y resolution.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const RESOLUTION_UNIT                                   = 0x0128;

  /**
   * Transfer function.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 3.
   */
  const TRANSFER_FUNCTION                                 = 0x012D;

  /**
   * Software used.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: any number.
   */
  const SOFTWARE                                          = 0x0131;

  /**
   * File change date and time.
   *
   * Format: {@link PelFormat::ASCII}, modelled by the {@link
   * PelEntryTime} class.
   *
   * Components: 20.
   */
  const DATE_TIME                                         = 0x0132;

  /**
   * Person who created the image.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: any number.
   */
  const ARTIST                                            = 0x013B;

  /**
   * White point chromaticity.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 2.
   */
  const WHITE_POINT                                       = 0x013E;

  /**
   * Chromaticities of primaries.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 6.
   */
  const PRIMARY_CHROMATICITIES                            = 0x013F;

  /**
   * Transfer Range
   *
   * Format: Unknown.
   *
   * Components: Unknown.
   */
  const TRANSFER_RANGE                                    = 0x0156;

  /**
   * JPEGProc
   *
   * Format: Unknown.
   *
   * Components: Unknown.
   */
  const JPEG_PROC                                         = 0x0200;

  /**
   * Offset to JPEG SOI.
   *
   * Format: {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const JPEG_INTERCHANGE_FORMAT                           = 0x0201;

  /**
   * Bytes of JPEG data.
   *
   * Format: {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const JPEG_INTERCHANGE_FORMAT_LENGTH                    = 0x0202;

  /**
   * Color space transformation matrix coefficients.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 3.
   */
  const YCBCR_COEFFICIENTS                                = 0x0211;

  /**
   * Subsampling ratio of Y to C.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 2.
   */
  const YCBCR_SUB_SAMPLING                                = 0x0212;

  /**
   * Y and C positioning.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const YCBCR_POSITIONING                                 = 0x0213;

  /**
   * Pair of black and white reference values.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 6.
   */
  const REFERENCE_BLACK_WHITE                             = 0x0214;

  /**
   * Related Image File Format
   *
   * Format: Unknown.
   *
   * Components: Unknown.
   */
  const RELATED_IMAGE_FILE_FORMAT                         = 0x1000;

  /**
   * Related Image Width
   *
   * Format: Unknown, probably {@link PelFormat::SHORT}?
   *
   * Components: Unknown, probably 1.
   */
  const RELATED_IMAGE_WIDTH                               = 0x1001;

  /** Related Image Length
   *
   * Format: Unknown, probably {@link PelFormat::SHORT}?
   *
   * Components: Unknown, probably 1.
   */
  const RELATED_IMAGE_LENGTH                              = 0x1002;

  /**
   * CFA Repeat Pattern Dim.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 2.
   */
  const CFA_REPEAT_PATTERN_DIM                            = 0x828D;

  /**
   * Battery level.
   *
   * Format: Unknown.
   *
   * Components: Unknown.
   */
  const BATTERY_LEVEL                                     = 0x828F;

  /**
   * Copyright holder.
   *
   * Format: {@link PelFormat::ASCII}, modelled by the {@link
   * PelEntryCopyright} class.
   *
   * Components: any number.
   */
  const COPYRIGHT                                         = 0x8298;

  /**
   * Exposure Time
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const EXPOSURE_TIME                                     = 0x829A;

  /**
   * FNumber
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const FNUMBER                                           = 0x829D;

  /**
   * IPTC/NAA
   *
   * Format: {@link PelFormat::LONG}.
   *
   * Components: any number.
   */
  const IPTC_NAA                                          = 0x83BB;

  /**
   * Exif IFD Pointer
   *
   * Format: {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const EXIF_IFD_POINTER                                  = 0x8769;

  /**
   * Inter Color Profile
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: any number.
   */
  const INTER_COLOR_PROFILE                               = 0x8773;

  /**
   * Exposure Program
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const EXPOSURE_PROGRAM                                  = 0x8822;

  /**
   * Spectral Sensitivity
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: any number.
   */
  const SPECTRAL_SENSITIVITY                              = 0x8824;

  /**
   * GPS Info IFD Pointer
   *
   * Format: {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const GPS_INFO_IFD_POINTER                              = 0x8825;

  /**
   * ISO Speed Ratings
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 2.
   */
  const ISO_SPEED_RATINGS                                 = 0x8827;

  /**
   * OECF
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: any number.
   */
  const OECF                                              = 0x8828;

  /**
   * Exif version.
   *
   * Format: {@link PelFormat::UNDEFINED}, modelled by the {@link
   * PelEntryVersion} class.
   *
   * Components: 4.
   */
  const EXIF_VERSION                                      = 0x9000;

  /**
   * Date and time of original data generation.
   *
   * Format: {@link PelFormat::ASCII}, modelled by the {@link
   * PelEntryTime} class.
   *
   * Components: 20.
   */
  const DATE_TIME_ORIGINAL                                = 0x9003;

  /**
   * Date and time of digital data generation.
   *
   * Format: {@link PelFormat::ASCII}, modelled by the {@link
   * PelEntryTime} class.
   *
   * Components: 20.
   */
  const DATE_TIME_DIGITIZED                               = 0x9004;

  /**
   * Meaning of each component.
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: 4.
   */
  const COMPONENTS_CONFIGURATION                          = 0x9101;

  /**
   * Image compression mode.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const COMPRESSED_BITS_PER_PIXEL                         = 0x9102;

  /**
   * Shutter speed
   *
   * Format: {@link PelFormat::SRATIONAL}.
   *
   * Components: 1.
   */
  const SHUTTER_SPEED_VALUE                               = 0x9201;

  /**
   * Aperture
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const APERTURE_VALUE                                    = 0x9202;

  /**
   * Brightness
   *
   * Format: {@link PelFormat::SRATIONAL}.
   *
   * Components: 1.
   */
  const BRIGHTNESS_VALUE                                  = 0x9203;

  /**
   * Exposure Bias
   *
   * Format: {@link PelFormat::SRATIONAL}.
   *
   * Components: 1.
   */
  const EXPOSURE_BIAS_VALUE                               = 0x9204;

  /**
   * Max Aperture Value
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const MAX_APERTURE_VALUE                                = 0x9205;

  /**
   * Subject Distance
   *
   * Format: {@link PelFormat::SRATIONAL}.
   *
   * Components: 1.
   */
  const SUBJECT_DISTANCE                                  = 0x9206;

  /**
   * Metering Mode
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const METERING_MODE                                     = 0x9207;

  /**
   * Light Source
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const LIGHT_SOURCE                                      = 0x9208;

  /**
   * Flash
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const FLASH                                             = 0x9209;

  /**
   * Focal Length
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const FOCAL_LENGTH                                      = 0x920A;

  /**
   * Subject Area
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 4.
   */
  const SUBJECT_AREA                                      = 0x9214;

  /**
   * Maker Note
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: any number.
   */
  const MAKER_NOTE                                        = 0x927C;

  /**
   * User Comment
   *
   * Format: {@link PelFormat::UNDEFINED}, modelled by the {@link
   * PelEntryUserComment} class.
   *
   * Components: any number.
   */
  const USER_COMMENT                                      = 0x9286;

  /**
   * SubSec Time
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: any number.
   */
  const SUB_SEC_TIME                                      = 0x9290;

  /**
   * SubSec Time Original
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: any number.
   */
  const SUB_SEC_TIME_ORIGINAL                             = 0x9291;

  /**
   * SubSec Time Digitized
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: any number.
   */
  const SUB_SEC_TIME_DIGITIZED                            = 0x9292;

  /**
   * Windows XP Title
   *
   * Format: {@link PelFormat::BYTE}.
   *
   * Components: any number.
   */
  const XP_TITLE                                          = 0x9C9B;


  /**
   * Windows XP Comment
   *
   * Format: {@link PelFormat::BYTE}.
   *
   * Components: any number.
   */
  const XP_COMMENT                                        = 0x9C9C;


  /**
   * Windows XP Author
   *
   * Format: {@link PelFormat::BYTE}.
   *
   * Components: any number.
   */
  const XP_AUTHOR                                         = 0x9C9D;


  /**
   * Windows XP Keywords
   *
   * Format: {@link PelFormat::BYTE}.
   *
   * Components: any number.
   */
  const XP_KEYWORDS                                       = 0x9C9E;


  /**
   * Windows XP Subject
   *
   * Format: {@link PelFormat::BYTE}.
   *
   * Components: any number.
   */
  const XP_SUBJECT                                        = 0x9C9F;


  /**
   * Supported Flashpix version
   *
   * Format: {@link PelFormat::UNDEFINED}, modelled by the {@link
   * PelEntryVersion} class.
   *
   * Components: 4.
   */
  const FLASH_PIX_VERSION                                 = 0xA000;

  /**
   * Color space information.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const COLOR_SPACE                                       = 0xA001;

  /**
   * Valid image width.
   *
   * Format: {@link PelFormat::SHORT} or {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const PIXEL_X_DIMENSION                                 = 0xA002;

  /**
   * Valid image height.
   *
   * Format: {@link PelFormat::SHORT} or {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const PIXEL_Y_DIMENSION                                 = 0xA003;

  /**
   * Related audio file.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: any number.
   */
  const RELATED_SOUND_FILE                                = 0xA004;

  /**
   * Interoperability IFD Pointer
   *
   * Format: {@link PelFormat::LONG}.
   *
   * Components: 1.
   */
  const INTEROPERABILITY_IFD_POINTER                      = 0xA005;

  /**
   * Flash energy.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const FLASH_ENERGY                                      = 0xA20B;

  /**
   * Spatial frequency response.
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: any number.
   */
  const SPATIAL_FREQUENCY_RESPONSE                        = 0xA20C;

  /**
   * Focal plane X resolution.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const FOCAL_PLANE_X_RESOLUTION                          = 0xA20E;

  /**
   * Focal plane Y resolution.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const FOCAL_PLANE_Y_RESOLUTION                          = 0xA20F;

  /**
   * Focal plane resolution unit.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const FOCAL_PLANE_RESOLUTION_UNIT                       = 0xA210;

  /**
   * Subject location.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const SUBJECT_LOCATION                                  = 0xA214;

  /**
   * Exposure index.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const EXPOSURE_INDEX                                    = 0xA215;

  /**
   * Sensing method.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const SENSING_METHOD                                    = 0xA217;

  /**
   * File source.
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: 1.
   */
  const FILE_SOURCE                                       = 0xA300;

  /**
   * Scene type.
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: 1.
   */
  const SCENE_TYPE                                        = 0xA301;

  /**
   * CFA pattern.
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: any number.
   */
  const CFA_PATTERN                                       = 0xA302;

  /**
   * Custom image processing.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const CUSTOM_RENDERED                                   = 0xA401;

  /**
   * Exposure mode.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const EXPOSURE_MODE                                     = 0xA402;

  /**
   * White balance.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const WHITE_BALANCE                                     = 0xA403;

  /**
   * Digital zoom ratio.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const DIGITAL_ZOOM_RATIO                                = 0xA404;

  /**
   * Focal length in 35mm film.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const FOCAL_LENGTH_IN_35MM_FILM      = 0xA405;

  /**
   * Scene capture type.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const SCENE_CAPTURE_TYPE                                = 0xA406;

  /**
   * Gain control.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const GAIN_CONTROL                                      = 0xA407;

  /**
   * Contrast.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const CONTRAST                                          = 0xA408;

  /**
   * Saturation.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const SATURATION                                        = 0xA409;

  /**
   * Sharpness.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const SHARPNESS                                         = 0xA40A;

  /**
   * Device settings description.
   *
   * This tag indicates information on the picture-taking conditions
   * of a particular camera model.  The tag is used only to indicate
   * the picture-taking conditions in the reader.
   */
  const DEVICE_SETTING_DESCRIPTION                        = 0xA40B;

  /**
   * Subject distance range.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const SUBJECT_DISTANCE_RANGE                            = 0xA40C;

  /**
   * Image unique ID.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 32.
   */
  const IMAGE_UNIQUE_ID                                   = 0xA420;

  /**
   * Gamma.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const GAMMA                                             = 0xA500;

  /**
   * PrintIM
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: unknown.
   */
  const PRINT_IM                                          = 0xC4A5;

  /**
   * GPS tag version.
   *
   * Format: {@link PelFormat::BYTE}.
   *
   * Components: 4.
   */
  const GPS_VERSION_ID                                    = 0x0000;

  /**
   * North or South Latitude.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_LATITUDE_REF                                  = 0x0001;

  /**
   * Latitude.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 3.
   */
  const GPS_LATITUDE                                      = 0x0002;

  /**
   * East or West Longitude.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_LONGITUDE_REF                                 = 0x0003;

  /**
   * Longitude.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 3.
   */
  const GPS_LONGITUDE                                     = 0x0004;

  /**
   * Altitude reference.
   *
   * Format: {@link PelFormat::BYTE}.
   *
   * Components: 1.
   */
  const GPS_ALTITUDE_REF                                  = 0x0005;

  /**
   * Altitude.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const GPS_ALTITUDE                                      = 0x0006;

  /**
   * GPS time (atomic clock).
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 3.
   */
  const GPS_TIME_STAMP                                    = 0x0007;

  /**
   * GPS satellites used for measurement.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: Any.
   */
  const GPS_SATELLITES                                    = 0x0008;

  /**
   * GPS receiver status.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_STATUS                                        = 0x0009;

  /**
   * GPS measurement mode.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_MEASURE_MODE                                  = 0x000A;

  /**
   * Measurement precision.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const GPS_DOP                                           = 0x000B;

  /**
   * Speed unit.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_SPEED_REF                                     = 0x000C;

  /**
   * Speed of GPS receiver.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const GPS_SPEED                                         = 0x000D;

  /**
   * Reference for direction of movement.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_TRACK_REF                                     = 0x000E;

  /**
   * Direction of movement.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const GPS_TRACK                                         = 0x000F;

  /**
   * Reference for direction of image.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_IMG_DIRECTION_REF                             = 0x0010;

  /**
   * Direction of image.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const GPS_IMG_DIRECTION                                 = 0x0011;

  /**
   * Geodetic survey data used.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: Any.
   */
  const GPS_MAP_DATUM                                     = 0x0012;

  /**
   * Reference for latitude of destination.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_DEST_LATITUDE_REF                             = 0x0013;

  /**
   * Latitude of destination.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 3.
   */
  const GPS_DEST_LATITUDE                                 = 0x0014;

  /**
   * Reference for longitude of destination.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_DEST_LONGITUDE_REF                            = 0x0015;

  /**
   * Longitude of destination.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 3.
   */
  const GPS_DEST_LONGITUDE                                = 0x0016;

  /**
   * Reference for bearing of destination.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_DEST_BEARING_REF                              = 0x0017;

  /**
   * Bearing of destination.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const GPS_DEST_BEARING                                  = 0x0018;

  /**
   * Reference for distance to destination.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 2.
   */
  const GPS_DEST_DISTANCE_REF                             = 0x0019;

  /**
   * Distance to destination.
   *
   * Format: {@link PelFormat::RATIONAL}.
   *
   * Components: 1.
   */
  const GPS_DEST_DISTANCE                                 = 0x001A;

  /**
   * Name of GPS processing method.
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: Any.
   */
  const GPS_PROCESSING_METHOD                             = 0x001B;

  /**
   * Name of GPS area.
   *
   * Format: {@link PelFormat::UNDEFINED}.
   *
   * Components: Any.
   */
  const GPS_AREA_INFORMATION                              = 0x001C;

  /**
   * GPS date.
   *
   * Format: {@link PelFormat::ASCII}.
   *
   * Components: 11.
   */
  const GPS_DATE_STAMP                                    = 0x001D;

  /**
   * GPS differential correction.
   *
   * Format: {@link PelFormat::SHORT}.
   *
   * Components: 1.
   */
  const GPS_DIFFERENTIAL                                  = 0x001E;


  /**
   * Returns a short name for an Exif tag.
   *
   * @param int the IFD type of the tag, one of {@link PelIfd::IFD0},
   * {@link PelIfd::IFD1}, {@link PelIfd::EXIF}, {@link PelIfd::GPS},
   * or {@link PelIfd::INTEROPERABILITY}.
   *
   * @param PelTag the tag.
   *
   * @return string the short name of the tag, e.g., 'ImageWidth' for
   * the {@link IMAGE_WIDTH} tag.  If the tag is not known, the string
   * 'Unknown:0xTTTT' will be returned where 'TTTT' is the hexadecimal
   * representation of the tag.
   */
  static function getName($type, $tag) {

    switch ($type) {
    case PelIfd::IFD0:
    case PelIfd::IFD1:
    case PelIfd::EXIF:
    case PelIfd::INTEROPERABILITY:

      switch ($tag) {
      case self::INTEROPERABILITY_INDEX:
        return 'InteroperabilityIndex';
      case self::INTEROPERABILITY_VERSION:
        return 'InteroperabilityVersion';
      case self::IMAGE_WIDTH:
        return 'ImageWidth';
      case self::IMAGE_LENGTH:
        return 'ImageLength';
      case self::BITS_PER_SAMPLE:
        return 'BitsPerSample';
      case self::COMPRESSION:
        return 'Compression';
      case self::PHOTOMETRIC_INTERPRETATION:
        return 'PhotometricInterpretation';
      case self::FILL_ORDER:
        return 'FillOrder';
      case self::DOCUMENT_NAME:
        return 'DocumentName';
      case self::IMAGE_DESCRIPTION:
        return 'ImageDescription';
      case self::MAKE:
        return 'Make';
      case self::MODEL:
        return 'Model';
      case self::STRIP_OFFSETS:
        return 'StripOffsets';
      case self::ORIENTATION:
        return 'Orientation';
      case self::SAMPLES_PER_PIXEL:
        return 'SamplesPerPixel';
      case self::ROWS_PER_STRIP:
        return 'RowsPerStrip';
      case self::STRIP_BYTE_COUNTS:
        return 'StripByteCounts';
      case self::X_RESOLUTION:
        return 'XResolution';
      case self::Y_RESOLUTION:
        return 'YResolution';
      case self::PLANAR_CONFIGURATION:
        return 'PlanarConfiguration';
      case self::RESOLUTION_UNIT:
        return 'ResolutionUnit';
      case self::TRANSFER_FUNCTION:
        return 'TransferFunction';
      case self::SOFTWARE:
        return 'Software';
      case self::DATE_TIME:
        return 'DateTime';
      case self::ARTIST:
        return 'Artist';
      case self::WHITE_POINT:
        return 'WhitePoint';
      case self::PRIMARY_CHROMATICITIES:
        return 'PrimaryChromaticities';
      case self::TRANSFER_RANGE:
        return 'TransferRange';
      case self::JPEG_PROC:
        return 'JPEGProc';
      case self::JPEG_INTERCHANGE_FORMAT:
        return 'JPEGInterchangeFormat';
      case self::JPEG_INTERCHANGE_FORMAT_LENGTH:
        return 'JPEGInterchangeFormatLength';
      case self::YCBCR_COEFFICIENTS:
        return 'YCbCrCoefficients';
      case self::YCBCR_SUB_SAMPLING:
        return 'YCbCrSubSampling';
      case self::YCBCR_POSITIONING:
        return 'YCbCrPositioning';
      case self::REFERENCE_BLACK_WHITE:
        return 'ReferenceBlackWhite';
      case self::RELATED_IMAGE_FILE_FORMAT:
        return 'RelatedImageFileFormat';
      case self::RELATED_IMAGE_WIDTH:
        return 'RelatedImageWidth';
      case self::RELATED_IMAGE_LENGTH:
        return 'RelatedImageLength';
      case self::CFA_REPEAT_PATTERN_DIM:
        return 'CFARepeatPatternDim';
      case self::CFA_PATTERN:
        return 'CFAPattern';
      case self::BATTERY_LEVEL:
        return 'BatteryLevel';
      case self::COPYRIGHT:
        return 'Copyright';
      case self::EXPOSURE_TIME:
        return 'ExposureTime';
      case self::FNUMBER:
        return 'FNumber';
      case self::IPTC_NAA:
        return 'IPTC/NAA';
      case self::EXIF_IFD_POINTER:
        return 'ExifIFDPointer';
      case self::INTER_COLOR_PROFILE:
        return 'InterColorProfile';
      case self::EXPOSURE_PROGRAM:
        return 'ExposureProgram';
      case self::SPECTRAL_SENSITIVITY:
        return 'SpectralSensitivity';
      case self::GPS_INFO_IFD_POINTER:
        return 'GPSInfoIFDPointer';
      case self::ISO_SPEED_RATINGS:
        return 'ISOSpeedRatings';
      case self::OECF:
        return 'OECF';
      case self::EXIF_VERSION:
        return 'ExifVersion';
      case self::DATE_TIME_ORIGINAL:
        return 'DateTimeOriginal';
      case self::DATE_TIME_DIGITIZED:
        return 'DateTimeDigitized';
      case self::COMPONENTS_CONFIGURATION:
        return 'ComponentsConfiguration';
      case self::COMPRESSED_BITS_PER_PIXEL:
        return 'CompressedBitsPerPixel';
      case self::SHUTTER_SPEED_VALUE:
        return 'ShutterSpeedValue';
      case self::APERTURE_VALUE:
        return 'ApertureValue';
      case self::BRIGHTNESS_VALUE:
        return 'BrightnessValue';
      case self::EXPOSURE_BIAS_VALUE:
        return 'ExposureBiasValue';
      case self::MAX_APERTURE_VALUE:
        return 'MaxApertureValue';
      case self::SUBJECT_DISTANCE:
        return 'SubjectDistance';
      case self::METERING_MODE:
        return 'MeteringMode';
      case self::LIGHT_SOURCE:
        return 'LightSource';
      case self::FLASH:
        return 'Flash';
      case self::FOCAL_LENGTH:
        return 'FocalLength';
      case self::MAKER_NOTE:
        return 'MakerNote';
      case self::USER_COMMENT:
        return 'UserComment';
      case self::SUB_SEC_TIME:
        return 'SubSecTime';
      case self::SUB_SEC_TIME_ORIGINAL:
        return 'SubSecTimeOriginal';
      case self::SUB_SEC_TIME_DIGITIZED:
        return 'SubSecTimeDigitized';
      case self::XP_TITLE:
        return 'WindowsXPTitle';
      case self::XP_COMMENT:
        return 'WindowsXPComment';
      case self::XP_AUTHOR:
        return 'WindowsXPAuthor';
      case self::XP_KEYWORDS:
        return 'WindowsXPKeywords';
      case self::XP_SUBJECT:
        return 'WindowsXPSubject';
      case self::FLASH_PIX_VERSION:
        return 'FlashPixVersion';
      case self::COLOR_SPACE:
        return 'ColorSpace';
      case self::PIXEL_X_DIMENSION:
        return 'PixelXDimension';
      case self::PIXEL_Y_DIMENSION:
        return 'PixelYDimension';
      case self::RELATED_SOUND_FILE:
        return 'RelatedSoundFile';
      case self::INTEROPERABILITY_IFD_POINTER:
        return 'InteroperabilityIFDPointer';
      case self::FLASH_ENERGY:
        return 'FlashEnergy';
      case self::SPATIAL_FREQUENCY_RESPONSE:
        return 'SpatialFrequencyResponse';
      case self::FOCAL_PLANE_X_RESOLUTION:
        return 'FocalPlaneXResolution';
      case self::FOCAL_PLANE_Y_RESOLUTION:
        return 'FocalPlaneYResolution';
      case self::FOCAL_PLANE_RESOLUTION_UNIT:
        return 'FocalPlaneResolutionUnit';
      case self::SUBJECT_LOCATION:
        return 'SubjectLocation';
      case self::EXPOSURE_INDEX:
        return 'ExposureIndex';
      case self::SENSING_METHOD:
        return 'SensingMethod';
      case self::FILE_SOURCE:
        return 'FileSource';
      case self::SCENE_TYPE:
        return 'SceneType';
      case self::SUBJECT_AREA:
        return 'SubjectArea';
      case self::CUSTOM_RENDERED:
        return 'CustomRendered';
      case self::EXPOSURE_MODE:
        return 'ExposureMode';
      case self::WHITE_BALANCE:
        return 'WhiteBalance';
      case self::DIGITAL_ZOOM_RATIO:
        return 'DigitalZoomRatio';
      case self::FOCAL_LENGTH_IN_35MM_FILM:
        return 'FocalLengthIn35mmFilm';
      case self::SCENE_CAPTURE_TYPE:
        return 'SceneCaptureType';
      case self::GAIN_CONTROL:
        return 'GainControl';
      case self::CONTRAST:
        return 'Contrast';
      case self::SATURATION:
        return 'Saturation';
      case self::SHARPNESS:
        return 'Sharpness';
      case self::DEVICE_SETTING_DESCRIPTION:
        return 'DeviceSettingDescription';
      case self::SUBJECT_DISTANCE_RANGE:
        return 'SubjectDistanceRange';
      case self::IMAGE_UNIQUE_ID:
        return 'ImageUniqueID';
      case self::GAMMA:
        return 'Gamma';
      case self::PRINT_IM:
        return 'PrintIM';
      }

    case PelIfd::GPS:
      switch ($tag) {
      case self::GPS_VERSION_ID:
        return 'GPSVersionID';
      case self::GPS_LATITUDE_REF:
        return 'GPSLatitudeRef';
      case self::GPS_LATITUDE:
        return 'GPSLatitude';
      case self::GPS_LONGITUDE_REF:
        return 'GPSLongitudeRef';
      case self::GPS_LONGITUDE:
        return 'GPSLongitude';
      case self::GPS_ALTITUDE_REF:
        return 'GPSAltitudeRef';
      case self::GPS_ALTITUDE:
        return 'GPSAltitude';
      case self::GPS_TIME_STAMP:
        return 'GPSTimeStamp';
      case self::GPS_SATELLITES:
        return 'GPSSatellites';
      case self::GPS_STATUS:
        return 'GPSStatus';
      case self::GPS_MEASURE_MODE:
        return 'GPSMeasureMode';
      case self::GPS_DOP:
        return 'GPSDOP';
      case self::GPS_SPEED_REF:
        return 'GPSSpeedRef';
      case self::GPS_SPEED:
        return 'GPSSpeed';
      case self::GPS_TRACK_REF:
        return 'GPSTrackRef';
      case self::GPS_TRACK:
        return 'GPSTrack';
      case self::GPS_IMG_DIRECTION_REF:
        return 'GPSImgDirectionRef';
      case self::GPS_IMG_DIRECTION:
        return 'GPSImgDirection';
      case self::GPS_MAP_DATUM:
        return 'GPSMapDatum';
      case self::GPS_DEST_LATITUDE_REF:
        return 'GPSDestLatitudeRef';
      case self::GPS_DEST_LATITUDE:
        return 'GPSDestLatitude';
      case self::GPS_DEST_LONGITUDE_REF:
        return 'GPSDestLongitudeRef';
      case self::GPS_DEST_LONGITUDE:
        return 'GPSDestLongitude';
      case self::GPS_DEST_BEARING_REF:
        return 'GPSDestBearingRef';
      case self::GPS_DEST_BEARING:
        return 'GPSDestBearing';
      case self::GPS_DEST_DISTANCE_REF:
        return 'GPSDestDistanceRef';
      case self::GPS_DEST_DISTANCE:
        return 'GPSDestDistance';
      case self::GPS_PROCESSING_METHOD:
        return 'GPSProcessingMethod';
      case self::GPS_AREA_INFORMATION:
        return 'GPSAreaInformation';
      case self::GPS_DATE_STAMP:
        return 'GPSDateStamp';
      case self::GPS_DIFFERENTIAL:
        return 'GPSDifferential';
      }

    default:
      return Pel::fmt('Unknown: 0x%04X', $tag);
    }
  }


  /**
   * Returns a title for an Exif tag.
   *
   * @param int the IFD type of the tag, one of {@link PelIfd::IFD0},
   * {@link PelIfd::IFD1}, {@link PelIfd::EXIF}, {@link PelIfd::GPS},
   * or {@link PelIfd::INTEROPERABILITY}.
   *
   * @param PelTag the tag.
   *
   * @return string the title of the tag, e.g., 'Image Width' for the
   * {@link IMAGE_WIDTH} tag.  If the tag isn't known, the string
   * 'Unknown Tag: 0xTT' will be returned where 'TT' is the
   * hexadecimal representation of the tag.
   */
  function getTitle($type, $tag) {

    switch ($type) {
    case PelIfd::IFD0:
    case PelIfd::IFD1:
    case PelIfd::EXIF:
    case PelIfd::INTEROPERABILITY:

      switch ($tag) {
      case self::INTEROPERABILITY_INDEX:
        return Pel::tra('Interoperability Index');
      case self::INTEROPERABILITY_VERSION:
        return Pel::tra('Interoperability Version');
      case self::IMAGE_WIDTH:
        return Pel::tra('Image Width');
      case self::IMAGE_LENGTH:
        return Pel::tra('Image Length');
      case self::BITS_PER_SAMPLE:
        return Pel::tra('Bits per Sample');
      case self::COMPRESSION:
        return Pel::tra('Compression');
      case self::PHOTOMETRIC_INTERPRETATION:
        return Pel::tra('Photometric Interpretation');
      case self::FILL_ORDER:
        return Pel::tra('Fill Order');
      case self::DOCUMENT_NAME:
        return Pel::tra('Document Name');
      case self::IMAGE_DESCRIPTION:
        return Pel::tra('Image Description');
      case self::MAKE:
        return Pel::tra('Manufacturer');
      case self::MODEL:
        return Pel::tra('Model');
      case self::STRIP_OFFSETS:
        return Pel::tra('Strip Offsets');
      case self::ORIENTATION:
        return Pel::tra('Orientation');
      case self::SAMPLES_PER_PIXEL:
        return Pel::tra('Samples per Pixel');
      case self::ROWS_PER_STRIP:
        return Pel::tra('Rows per Strip');
      case self::STRIP_BYTE_COUNTS:
        return Pel::tra('Strip Byte Count');
      case self::X_RESOLUTION:
        return Pel::tra('x-Resolution');
      case self::Y_RESOLUTION:
        return Pel::tra('y-Resolution');
      case self::PLANAR_CONFIGURATION:
        return Pel::tra('Planar Configuration');
      case self::RESOLUTION_UNIT:
        return Pel::tra('Resolution Unit');
      case self::TRANSFER_FUNCTION:
        return Pel::tra('Transfer Function');
      case self::SOFTWARE:
        return Pel::tra('Software');
      case self::DATE_TIME:
        return Pel::tra('Date and Time');
      case self::ARTIST:
        return Pel::tra('Artist');
      case self::WHITE_POINT:
        return Pel::tra('White Point');
      case self::PRIMARY_CHROMATICITIES:
        return Pel::tra('Primary Chromaticities');
      case self::TRANSFER_RANGE:
        return Pel::tra('Transfer Range');
      case self::JPEG_PROC:
        return Pel::tra('JPEG Process');
      case self::JPEG_INTERCHANGE_FORMAT:
        return Pel::tra('JPEG Interchange Format');
      case self::JPEG_INTERCHANGE_FORMAT_LENGTH:
        return Pel::tra('JPEG Interchange Format Length');
      case self::YCBCR_COEFFICIENTS:
        return Pel::tra('YCbCr Coefficients');
      case self::YCBCR_SUB_SAMPLING:
        return Pel::tra('YCbCr Sub-Sampling');
      case self::YCBCR_POSITIONING:
        return Pel::tra('YCbCr Positioning');
      case self::REFERENCE_BLACK_WHITE:
        return Pel::tra('Reference Black/White');
      case self::RELATED_IMAGE_FILE_FORMAT:
        return Pel::tra('Related Image File Format');
      case self::RELATED_IMAGE_WIDTH:
        return Pel::tra('Related Image Width');
      case self::RELATED_IMAGE_LENGTH:
        return Pel::tra('Related Image Length');
      case self::CFA_REPEAT_PATTERN_DIM:
        return Pel::tra('CFA Repeat Pattern Dim');
      case self::CFA_PATTERN:
        return Pel::tra('CFA Pattern');
      case self::BATTERY_LEVEL:
        return Pel::tra('Battery Level');
      case self::COPYRIGHT:
        return Pel::tra('Copyright');
      case self::EXPOSURE_TIME:
        return Pel::tra('Exposure Time');
      case self::FNUMBER:
        return Pel::tra('FNumber');
      case self::IPTC_NAA:
        return Pel::tra('IPTC/NAA');
      case self::EXIF_IFD_POINTER:
        return Pel::tra('Exif IFD Pointer');
      case self::INTER_COLOR_PROFILE:
        return Pel::tra('Inter Color Profile');
      case self::EXPOSURE_PROGRAM:
        return Pel::tra('Exposure Program');
      case self::SPECTRAL_SENSITIVITY:
        return Pel::tra('Spectral Sensitivity');
      case self::GPS_INFO_IFD_POINTER:
        return Pel::tra('GPS Info IFD Pointer');
      case self::ISO_SPEED_RATINGS:
        return Pel::tra('ISO Speed Ratings');
      case self::OECF:
        return Pel::tra('OECF');
      case self::EXIF_VERSION:
        return Pel::tra('Exif Version');
      case self::DATE_TIME_ORIGINAL:
        return Pel::tra('Date and Time (original)');
      case self::DATE_TIME_DIGITIZED:
        return Pel::tra('Date and Time (digitized)');
      case self::COMPONENTS_CONFIGURATION:
        return Pel::tra('Components Configuration');
      case self::COMPRESSED_BITS_PER_PIXEL:
        return Pel::tra('Compressed Bits per Pixel');
      case self::SHUTTER_SPEED_VALUE:
        return Pel::tra('Shutter speed');
      case self::APERTURE_VALUE:
        return Pel::tra('Aperture');
      case self::BRIGHTNESS_VALUE:
        return Pel::tra('Brightness');
      case self::EXPOSURE_BIAS_VALUE:
        return Pel::tra('Exposure Bias');
      case self::MAX_APERTURE_VALUE:
        return Pel::tra('Max Aperture Value');
      case self::SUBJECT_DISTANCE:
        return Pel::tra('Subject Distance');
      case self::METERING_MODE:
        return Pel::tra('Metering Mode');
      case self::LIGHT_SOURCE:
        return Pel::tra('Light Source');
      case self::FLASH:
        return Pel::tra('Flash');
      case self::FOCAL_LENGTH:
        return Pel::tra('Focal Length');
      case self::MAKER_NOTE:
        return Pel::tra('Maker Note');
      case self::USER_COMMENT:
        return Pel::tra('User Comment');
      case self::SUB_SEC_TIME:
        return Pel::tra('SubSec Time');
      case self::SUB_SEC_TIME_ORIGINAL:
        return Pel::tra('SubSec Time Original');
      case self::SUB_SEC_TIME_DIGITIZED:
        return Pel::tra('SubSec Time Digitized');
      case self::XP_TITLE:
        return 'Windows XP Title';
      case self::XP_COMMENT:
        return 'Windows XP Comment';
      case self::XP_AUTHOR:
        return 'Windows XP Author';
      case self::XP_KEYWORDS:
        return 'Windows XP Keywords';
      case self::XP_SUBJECT:
        return 'Windows XP Subject';
      case self::FLASH_PIX_VERSION:
        return Pel::tra('FlashPix Version');
      case self::COLOR_SPACE:
        return Pel::tra('Color Space');
      case self::PIXEL_X_DIMENSION:
        return Pel::tra('Pixel x-Dimension');
      case self::PIXEL_Y_DIMENSION:
        return Pel::tra('Pixel y-Dimension');
      case self::RELATED_SOUND_FILE:
        return Pel::tra('Related Sound File');
      case self::INTEROPERABILITY_IFD_POINTER:
        return Pel::tra('Interoperability IFD Pointer');
      case self::FLASH_ENERGY:
        return Pel::tra('Flash Energy');
      case self::SPATIAL_FREQUENCY_RESPONSE:
        return Pel::tra('Spatial Frequency Response');
      case self::FOCAL_PLANE_X_RESOLUTION:
        return Pel::tra('Focal Plane x-Resolution');
      case self::FOCAL_PLANE_Y_RESOLUTION:
        return Pel::tra('Focal Plane y-Resolution');
      case self::FOCAL_PLANE_RESOLUTION_UNIT:
        return Pel::tra('Focal Plane Resolution Unit');
      case self::SUBJECT_LOCATION:
        return Pel::tra('Subject Location');
      case self::EXPOSURE_INDEX:
        return Pel::tra('Exposure index');
      case self::SENSING_METHOD:
        return Pel::tra('Sensing Method');
      case self::FILE_SOURCE:
        return Pel::tra('File Source');
      case self::SCENE_TYPE:
        return Pel::tra('Scene Type');
      case self::SUBJECT_AREA:
        return Pel::tra('Subject Area');
      case self::CUSTOM_RENDERED:
        return Pel::tra('Custom Rendered');
      case self::EXPOSURE_MODE:
        return Pel::tra('Exposure Mode');
      case self::WHITE_BALANCE:
        return Pel::tra('White Balance');
      case self::DIGITAL_ZOOM_RATIO:
        return Pel::tra('Digital Zoom Ratio');
      case self::FOCAL_LENGTH_IN_35MM_FILM:
        return Pel::tra('Focal Length In 35mm Film');
      case self::SCENE_CAPTURE_TYPE:
        return Pel::tra('Scene Capture Type');
      case self::GAIN_CONTROL:
        return Pel::tra('Gain Control');
      case self::CONTRAST:
        return Pel::tra('Contrast');
      case self::SATURATION:
        return Pel::tra('Saturation');
      case self::SHARPNESS:
        return Pel::tra('Sharpness');
      case self::DEVICE_SETTING_DESCRIPTION:
        return Pel::tra('Device Setting Description');
      case self::SUBJECT_DISTANCE_RANGE:
        return Pel::tra('Subject Distance Range');
      case self::IMAGE_UNIQUE_ID:
        return Pel::tra('Image Unique ID');
      case self::GAMMA:
        return Pel::tra('Gamma');
      case self::PRINT_IM:
        return Pel::tra('Print IM');
      }

    case PelIfd::GPS:
      switch ($tag) {
      case self::GPS_VERSION_ID:
        return 'GPSVersionID';
      case self::GPS_LATITUDE_REF:
        return 'GPSLatitudeRef';
      case self::GPS_LATITUDE:
        return 'GPSLatitude';
      case self::GPS_LONGITUDE_REF:
        return 'GPSLongitudeRef';
      case self::GPS_LONGITUDE:
        return 'GPSLongitude';
      case self::GPS_ALTITUDE_REF:
        return 'GPSAltitudeRef';
      case self::GPS_ALTITUDE:
        return 'GPSAltitude';
      case self::GPS_TIME_STAMP:
        return 'GPSTimeStamp';
      case self::GPS_SATELLITES:
        return 'GPSSatellites';
      case self::GPS_STATUS:
        return 'GPSStatus';
      case self::GPS_MEASURE_MODE:
        return 'GPSMeasureMode';
      case self::GPS_DOP:
        return 'GPSDOP';
      case self::GPS_SPEED_REF:
        return 'GPSSpeedRef';
      case self::GPS_SPEED:
        return 'GPSSpeed';
      case self::GPS_TRACK_REF:
        return 'GPSTrackRef';
      case self::GPS_TRACK:
        return 'GPSTrack';
      case self::GPS_IMG_DIRECTION_REF:
        return 'GPSImgDirectionRef';
      case self::GPS_IMG_DIRECTION:
        return 'GPSImgDirection';
      case self::GPS_MAP_DATUM:
        return 'GPSMapDatum';
      case self::GPS_DEST_LATITUDE_REF:
        return 'GPSDestLatitudeRef';
      case self::GPS_DEST_LATITUDE:
        return 'GPSDestLatitude';
      case self::GPS_DEST_LONGITUDE_REF:
        return 'GPSDestLongitudeRef';
      case self::GPS_DEST_LONGITUDE:
        return 'GPSDestLongitude';
      case self::GPS_DEST_BEARING_REF:
        return 'GPSDestBearingRef';
      case self::GPS_DEST_BEARING:
        return 'GPSDestBearing';
      case self::GPS_DEST_DISTANCE_REF:
        return 'GPSDestDistanceRef';
      case self::GPS_DEST_DISTANCE:
        return 'GPSDestDistance';
      case self::GPS_PROCESSING_METHOD:
        return 'GPSProcessingMethod';
      case self::GPS_AREA_INFORMATION:
        return 'GPSAreaInformation';
      case self::GPS_DATE_STAMP:
        return 'GPSDateStamp';
      case self::GPS_DIFFERENTIAL:
        return 'GPSDifferential';
      }

    default:
      return Pel::fmt('Unknown Tag: 0x%04X', $tag);
    }
  }

}
?>