ExifPHPExtension.php

<?php

namespace Drupal\exif;

include_once drupal_get_path('module', 'exif') . '/ExifInterface.php';

/**
 * This is a helper class to handle the whole data processing of exif.
 */
class ExifPHPExtension implements ExifInterface {
    private static $instance = NULL;
    
    /**
     *
     *
     * @return object
     */
    public static function getInstance() {
        if (is_null(self::$instance)) {
            self::$instance = new self();
        }
        return self::$instance;
    }
    
    /**
     *
     *
     * @return array
     */
    public static function getMetadataSections() {
        $sections = array(
            'exif',
            'file',
            'computed',
            'ifd0',
            'gps',
            'winxp',
            'iptc',
            'xmp',
        );
        return $sections;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getMetadataFields(array $fields = array()) {
        $arSections = self::getMetadataSections();
        foreach ($fields as $drupal_field => $metadata_settings) {
            $metadata_field = $metadata_settings['metadata_field'];
            $ar = explode("_", $metadata_field);
            if (isset($ar[0]) && in_array($ar[0], $arSections)) {
                $section = $ar[0];
                unset($ar[0]);
                $fields[$drupal_field]['metadata_field'] = array(
                    'section' => $section,
                    'tag' => implode("_", $ar),
                );
            }
            else {
                // Remove from the list a non usable description.
                unset($fields[$drupal_field]);
                watchdog('exif', 'Not able to understand exif field settings !field', array(
                    '!field' => $metadata_field,
                ), WATCHDOG_WARNING);
            }
        }
        return $fields;
    }
    
    /**
     *
     *
     * @return bool
     */
    public static function checkConfiguration() {
        return function_exists('exif_read_data') && function_exists('iptcparse');
    }
    
    /**
     * Helper function to reformat fields where required.
     *
     * Some values (lat/lon) break down into structures, not strings.
     * Dates should be parsed nicely.
     *
     * @param array $data
     */
    public function _reformat(array $data) {
        // Make the key lowercase as field names must be.
        $data = array_change_key_case($data, CASE_LOWER);
        foreach ($data as $key => &$value) {
            if (is_array($value)) {
                $value = array_change_key_case($value, CASE_LOWER);
                switch ($key) {
                    // GPS values.
                    case 'gps_latitude':
                    case 'gps_longitude':
                    case 'gpslatitude':
                    case 'gpslongitude':
                        $value = $this->_exif_reformat_DMS2D($value, $data[$key . 'ref']);
                        break;
                }
            }
            else {
                if (is_string($value)) {
                    $value = trim($value);
                }
                if (!drupal_validate_utf8($value)) {
                    $value = utf8_encode($value);
                }
                switch ($key) {
                    // String values.
                    case 'usercomment':
                    case 'title':
                    case 'comment':
                    case 'author':
                    case 'subject':
                        if (strstartswith($value, 'UNICODE')) {
                            $value = substr($value, 8);
                        }
                        $value = $this->_exif_reencode_to_utf8($value);
                        break;
                    // Date values.
                    case 'filedatetime':
                        $value = date('c', $value);
                        break;
                    case 'datetimeoriginal':
                    case 'datetime':
                    case 'datetimedigitized':
                        // In case we get a datefield, we need to reformat it to the ISO
                        // 8601 standard which will look something like
                        // '2004-02-12T15:19:21'.
                        $date_time = explode(" ", $value);
                        $date_time[0] = str_replace(":", "-", $date_time[0]);
                        if (variable_get('exif_granularity', 0) == 1) {
                            $date_time[1] = "00:00:00";
                        }
                        $value = implode("T", $date_time);
                        break;
                    // GPS values.
                    case 'gpsaltitude':
                    case 'gpsimgdirection':
                        if (!isset($data[$key . 'ref'])) {
                            $data[$key . 'ref'] = 0;
                        }
                        $value = $this->_exif_reformat_DMS2D($value, $data[$key . 'ref']);
                        break;
                    case 'componentsconfiguration':
                    case 'compression':
                    case 'contrast':
                    case 'exposuremode':
                    case 'exposureprogram':
                    case 'flash':
                    case 'focalplaneresolutionunit':
                    case 'gaincontrol':
                    case 'lightsource':
                    case 'meteringmode':
                    case 'orientation':
                    case 'resolutionunit':
                    case 'saturation':
                    case 'scenecapturetype':
                    case 'sensingmethod':
                    case 'sensitivitytype':
                    case 'sharpness':
                    case 'subjectdistancerange':
                    case 'whitebalance':
                        $human_descriptions = $this->getHumanReadableDescriptions()[$key];
                        if (isset($human_descriptions[$value])) {
                            $value = $human_descriptions[$value];
                        }
                        break;
                    // Exposure values.
                    case 'exposuretime':
                        if (strpos($value, '/') !== FALSE) {
                            $value = $this->_normalise_fraction($value) . 's';
                        }
                        break;
                    // Focal Length values.
                    case 'focallength':
                        if (strpos($value, '/') !== FALSE) {
                            $value = $this->_normalise_fraction($value) . 'mm';
                        }
                        break;
                }
            }
        }
        return $data;
    }
    
    /**
     *
     *
     * @param string $value
     *
     * @return string
     */
    public function _exif_reencode_to_utf8($value) {
        $unicode_list = unpack("v*", $value);
        $result = "";
        foreach ($unicode_list as $key => $value) {
            if ($value != 0) {
                $one_character = pack("C", $value);
                $temp = mb_convert_encoding('&#' . $value . ';', 'UTF-8', 'HTML-ENTITIES');
                $result .= $temp;
            }
        }
        return $result;
    }
    
    /**
     * Normalise fractions.
     *
     * @param string
     *
     * @return string
     */
    public function _normalise_fraction($fraction) {
        $parts = explode('/', $fraction);
        $top = $parts[0];
        $bottom = $parts[1];
        if ($top > $bottom) {
            // Value > 1.
            if ($top % $bottom == 0) {
                $value = $top / $bottom;
            }
            else {
                $value = round($top / $bottom, 2);
            }
        }
        else {
            if ($top == $bottom) {
                // Value = 1.
                $value = '1';
            }
            else {
                // Value < 1.
                if ($top == 1) {
                    $value = '1/' . $bottom;
                }
                else {
                    if ($top != 0) {
                        $value = '1/' . round($bottom / $top, 0);
                    }
                    else {
                        $value = '0';
                    }
                }
            }
        }
        return $value;
    }
    
    /**
     * Helper function to change GPS co-ords into decimals.
     *
     * @param string|string $value
     * @param string $ref
     *
     * @return int
     */
    public function _exif_reformat_DMS2D($value, $ref) {
        if (!is_array($value)) {
            $value = array(
                $value,
            );
        }
        $dec = 0;
        $granularity = 0;
        foreach ($value as $element) {
            $parts = explode('/', $element);
            $dec += (double) ((double) $parts[0] / (double) $parts[1] / pow(60, $granularity));
            $granularity++;
        }
        if ($ref == 'S' || $ref == 'W') {
            $dec *= -1;
        }
        return $dec;
    }
    
    /**
     * {@inheritdoc}
     */
    public function readMetadataTags($file, $enable_sections = TRUE) {
        if (!file_exists($file)) {
            return array();
        }
        $data1 = $this->readExifTags($file, $enable_sections);
        $data2 = $this->readIPTCTags($file, $enable_sections);
        $data = array_merge($data1, $data2);
        if (is_array($data)) {
            foreach ($data as $section => $section_data) {
                $section_data = $this->_reformat($section_data);
                $data[$section] = $section_data;
            }
        }
        return $data;
    }
    
    /**
     *
     *
     * @param array $metadata
     * @param array $tag_names
     *
     * @return array
     */
    public function filterMetadataTags(array $metadata, array $tag_names) {
        $info = array();
        foreach ($tag_names as $drupal_field => $metadata_settings) {
            $tagName = $metadata_settings['metadata_field'];
            if (!empty($metadata[$tagName['section']][$tagName['tag']])) {
                $info[$tagName['section']][$tagName['tag']] = $metadata[$tagName['section']][$tagName['tag']];
            }
        }
        return $info;
    }
    
    /**
     * Read the Information from a picture according to the fields.
     *
     * @param string $file
     * @param bool $enable_sections
     *
     * @return array
     */
    public function readExifTags($file, $enable_sections = TRUE) {
        $supported_types = array(
            'jpg',
            'jpeg',
        );
        if (!in_array(strtolower($this->getFileType($file)), $supported_types)) {
            return array();
        }
        $exif = array();
        try {
            $exif = @exif_read_data($file, 0, $enable_sections);
        } catch (Exception $e) {
            watchdog('exif', 'Error while reading EXIF tags from image: !message', array(
                '!message' => $e->getMessage(),
            ), WATCHDOG_WARNING);
        }
        $arSmallExif = array();
        foreach ((array) $exif as $key1 => $value1) {
            if (is_array($value1)) {
                $value2 = array();
                foreach ((array) $value1 as $key3 => $value3) {
                    $value[strtolower($key3)] = $value3;
                }
            }
            else {
                $value = $value1;
            }
            $arSmallExif[strtolower($key1)] = $value;
        }
        return $arSmallExif;
    }
    
    /**
     *
     *
     * @param string $file
     *
     * @return string
     */
    private function getFileType($file) {
        $ar = explode('.', $file);
        $ending = $ar[count($ar) - 1];
        return $ending;
    }
    
    /**
     * Read IPTC tags.
     *
     * @param string $file
     *   Path to image to read IPTC from.
     * @param bool $enable_sections
     *
     * @return array
     */
    public function readIPTCTags($file, $enable_sections) {
        $humanReadableKey = $this->getHumanReadableIPTCkey();
        $infoImage = array();
        $size = getimagesize($file, $infoImage);
        $iptc = empty($infoImage["APP13"]) ? array() : iptcparse($infoImage["APP13"]);
        $arSmallIPTC = array();
        if (is_array($iptc)) {
            foreach ($iptc as $key => $value) {
                if (count($value) == 1) {
                    $resultTag = $value[0];
                }
                else {
                    $resultTag = $value;
                }
                if (array_key_exists($key, $humanReadableKey)) {
                    $humanKey = $humanReadableKey[$key];
                    $arSmallIPTC[$humanKey] = $resultTag;
                }
                else {
                    $arSmallIPTC[$key] = $resultTag;
                }
            }
        }
        if ($enable_sections) {
            return array(
                'iptc' => $arSmallIPTC,
            );
        }
        else {
            return $arSmallIPTC;
        }
    }
    
    /**
     *
     *
     * @return array
     */
    public function getHumanReadableExifKeys() {
        return array(
            "file_filename",
            "file_filedatetime",
            "file_filesize",
            "file_filetype",
            "file_mimetype",
            "file_sectionsfound",
            "computed_filename",
            "computed_filedatetime",
            "computed_filesize",
            "computed_filetype",
            "computed_mimetype",
            "computed_sectionsfound",
            "computed_html",
            "computed_height",
            "computed_width",
            "computed_iscolor",
            "computed_copyright",
            "computed_byteordermotorola",
            "computed_ccdwidth",
            "computed_aperturefnumber",
            "computed_usercomment",
            "computed_usercommentencoding",
            "computed_thumbnail.filetype",
            "computed_thumbnail.mimetype",
            "ifd0_filename",
            "ifd0_filedatetime",
            "ifd0_filesize",
            "ifd0_filetype",
            "ifd0_mimetype",
            "ifd0_sectionsfound",
            "ifd0_html",
            "ifd0_height",
            "ifd0_width",
            "ifd0_iscolor",
            "ifd0_byteordermotorola",
            "ifd0_ccdwidth",
            "ifd0_aperturefnumber",
            "ifd0_usercomment",
            "ifd0_usercommentencoding",
            "ifd0_thumbnail.filetype",
            "ifd0_thumbnail.mimetype",
            "ifd0_imagedescription",
            "ifd0_make",
            "ifd0_model",
            "ifd0_orientation",
            "ifd0_xresolution",
            "ifd0_yresolution",
            "ifd0_resolutionunit",
            "ifd0_software",
            "ifd0_datetime",
            "ifd0_artist",
            "ifd0_ycbcrpositioning",
            "ifd0_title",
            "ifd0_comments",
            "ifd0_author",
            "ifd0_subject",
            "ifd0_exif_ifd_pointer",
            "ifd0_gps_ifd_pointer",
            "thumbnail_filename",
            "thumbnail_filedatetime",
            "thumbnail_filesize",
            "thumbnail_filetype",
            "thumbnail_mimetype",
            "thumbnail_sectionsfound",
            "thumbnail_html",
            "thumbnail_height",
            "thumbnail_width",
            "thumbnail_iscolor",
            "thumbnail_byteordermotorola",
            "thumbnail_ccdwidth",
            "thumbnail_aperturefnumber",
            "thumbnail_usercomment",
            "thumbnail_usercommentencoding",
            "thumbnail_thumbnail.filetype",
            "thumbnail_thumbnail.mimetype",
            "thumbnail_imagedescription",
            "thumbnail_make",
            "thumbnail_model",
            "thumbnail_orientation",
            "thumbnail_xresolution",
            "thumbnail_yresolution",
            "thumbnail_resolutionunit",
            "thumbnail_software",
            "thumbnail_datetime",
            "thumbnail_artist",
            "thumbnail_ycbcrpositioning",
            "thumbnail_title",
            "thumbnail_comments",
            "thumbnail_author",
            "thumbnail_subject",
            "thumbnail_exif_ifd_pointer",
            "thumbnail_gps_ifd_pointer",
            "thumbnail_compression",
            "thumbnail_jpeginterchangeformat",
            "thumbnail_jpeginterchangeformatlength",
            "exif_filename",
            "exif_filedatetime",
            "exif_filesize",
            "exif_filetype",
            "exif_mimetype",
            "exif_sectionsfound",
            "exif_html",
            "exif_height",
            "exif_width",
            "exif_iscolor",
            "exif_byteordermotorola",
            "exif_ccdwidth",
            "exif_aperturefnumber",
            "exif_usercomment",
            "exif_usercommentencoding",
            "exif_thumbnail.filetype",
            "exif_thumbnail.mimetype",
            "exif_imagedescription",
            "exif_make",
            "exif_model",
            "exif_lens",
            "exif_lensid",
            "exif_orientation",
            "exif_xresolution",
            "exif_yresolution",
            "exif_resolutionunit",
            "exif_software",
            "exif_datetime",
            "exif_artist",
            "exif_ycbcrpositioning",
            "exif_title",
            "exif_comments",
            "exif_author",
            "exif_subject",
            "exif_exif_ifd_pointer",
            "exif_gps_ifd_pointer",
            "exif_compression",
            "exif_jpeginterchangeformat",
            "exif_jpeginterchangeformatlength",
            "exif_exposuretime",
            "exif_fnumber",
            "exif_exposureprogram",
            "exif_isospeedratings",
            "exif_exifversion",
            "exif_datetimeoriginal",
            "exif_datetimedigitized",
            "exif_componentsconfiguration",
            "exif_shutterspeedvalue",
            "exif_aperturevalue",
            "exif_exposurebiasvalue",
            "exif_meteringmode",
            "exif_flash",
            "exif_focallength",
            "exif_flashpixversion",
            "exif_colorspace",
            "exif_exifimagewidth",
            "exif_exifimagelength",
            "exif_interoperabilityoffset",
            "exif_focalplanexresolution",
            "exif_focalplaneyresolution",
            "exif_focalplaneresolutionunit",
            "exif_imageuniqueid",
            "gps_filename",
            "gps_filedatetime",
            "gps_filesize",
            "gps_filetype",
            "gps_mimetype",
            "gps_sectionsfound",
            "gps_html",
            "gps_height",
            "gps_width",
            "gps_iscolor",
            "gps_byteordermotorola",
            "gps_ccdwidth",
            "gps_aperturefnumber",
            "gps_usercomment",
            "gps_usercommentencoding",
            "gps_thumbnail.filetype",
            "gps_thumbnail.mimetype",
            "gps_imagedescription",
            "gps_make",
            "gps_model",
            "gps_orientation",
            "gps_xresolution",
            "gps_yresolution",
            "gps_resolutionunit",
            "gps_software",
            "gps_datetime",
            "gps_artist",
            "gps_ycbcrpositioning",
            "gps_title",
            "gps_comments",
            "gps_author",
            "gps_subject",
            "gps_exif_ifd_pointer",
            "gps_gps_ifd_pointer",
            "gps_compression",
            "gps_jpeginterchangeformat",
            "gps_jpeginterchangeformatlength",
            "gps_exposuretime",
            "gps_fnumber",
            "gps_exposureprogram",
            "gps_isospeedratings",
            "gps_exifversion",
            "gps_datetimeoriginal",
            "gps_datetimedigitized",
            "gps_componentsconfiguration",
            "gps_shutterspeedvalue",
            "gps_aperturevalue",
            "gps_exposurebiasvalue",
            "gps_meteringmode",
            "gps_flash",
            "gps_focallength",
            "gps_flashpixversion",
            "gps_colorspace",
            "gps_exifimagewidth",
            "gps_exifimagelength",
            "gps_interoperabilityoffset",
            "gps_gpsimgdirectionref",
            "gps_gpsimgdirection",
            "gps_focalplanexresolution",
            "gps_focalplaneyresolution",
            "gps_focalplaneresolutionunit",
            "gps_imageuniqueid",
            "gps_gpsversion",
            "gps_gpslatituderef",
            "gps_gpslatitude",
            "gps_gpslongituderef",
            "gps_gpslongitude",
            "gps_gpsaltituderef",
            "gps_gpsaltitude",
            "interop_filename",
            "interop_filedatetime",
            "interop_filesize",
            "interop_filetype",
            "interop_mimetype",
            "interop_sectionsfound",
            "interop_html",
            "interop_height",
            "interop_width",
            "interop_iscolor",
            "interop_byteordermotorola",
            "interop_ccdwidth",
            "interop_aperturefnumber",
            "interop_usercomment",
            "interop_usercommentencoding",
            "interop_thumbnail.filetype",
            "interop_thumbnail.mimetype",
            "interop_imagedescription",
            "interop_make",
            "interop_model",
            "interop_orientation",
            "interop_xresolution",
            "interop_yresolution",
            "interop_resolutionunit",
            "interop_software",
            "interop_datetime",
            "interop_artist",
            "interop_ycbcrpositioning",
            "interop_title",
            "interop_comments",
            "interop_author",
            "interop_subject",
            "interop_exif_ifd_pointer",
            "interop_gps_ifd_pointer",
            "interop_compression",
            "interop_jpeginterchangeformat",
            "interop_jpeginterchangeformatlength",
            "interop_exposuretime",
            "interop_fnumber",
            "interop_exposureprogram",
            "interop_isospeedratings",
            "interop_exifversion",
            "interop_datetimeoriginal",
            "interop_datetimedigitized",
            "interop_componentsconfiguration",
            "interop_shutterspeedvalue",
            "interop_aperturevalue",
            "interop_exposurebiasvalue",
            "interop_meteringmode",
            "interop_flash",
            "interop_focallength",
            "interop_flashpixversion",
            "interop_colorspace",
            "interop_exifimagewidth",
            "interop_exifimagelength",
            "interop_interoperabilityoffset",
            "interop_focalplanexresolution",
            "interop_focalplaneyresolution",
            "interop_focalplaneresolutionunit",
            "interop_imageuniqueid",
            "interop_gpsversion",
            "interop_gpslatituderef",
            "interop_gpslatitude",
            "interop_gpslongituderef",
            "interop_gpslongitude",
            "interop_gpsaltituderef",
            "interop_gpsaltitude",
            "interop_interoperabilityindex",
            "interop_interoperabilityversion",
            "winxp_filename",
            "winxp_filedatetime",
            "winxp_filesize",
            "winxp_filetype",
            "winxp_mimetype",
            "winxp_sectionsfound",
            "winxp_html",
            "winxp_height",
            "winxp_width",
            "winxp_iscolor",
            "winxp_byteordermotorola",
            "winxp_ccdwidth",
            "winxp_aperturefnumber",
            "winxp_usercomment",
            "winxp_usercommentencoding",
            "winxp_thumbnail.filetype",
            "winxp_thumbnail.mimetype",
            "winxp_imagedescription",
            "winxp_make",
            "winxp_model",
            "winxp_orientation",
            "winxp_xresolution",
            "winxp_yresolution",
            "winxp_resolutionunit",
            "winxp_software",
            "winxp_datetime",
            "winxp_artist",
            "winxp_ycbcrpositioning",
            "winxp_title",
            "winxp_comments",
            "winxp_author",
            "winxp_subject",
            "winxp_exif_ifd_pointer",
            "winxp_gps_ifd_pointer",
            "winxp_compression",
            "winxp_jpeginterchangeformat",
            "winxp_jpeginterchangeformatlength",
            "winxp_exposuretime",
            "winxp_fnumber",
            "winxp_exposureprogram",
            "winxp_isospeedratings",
            "winxp_exifversion",
            "winxp_datetimeoriginal",
            "winxp_datetimedigitized",
            "winxp_componentsconfiguration",
            "winxp_shutterspeedvalue",
            "winxp_aperturevalue",
            "winxp_exposurebiasvalue",
            "winxp_meteringmode",
            "winxp_flash",
            "winxp_focallength",
            "winxp_flashpixversion",
            "winxp_colorspace",
            "winxp_exifimagewidth",
            "winxp_exifimagelength",
            "winxp_interoperabilityoffset",
            "winxp_focalplanexresolution",
            "winxp_focalplaneyresolution",
            "winxp_focalplaneresolutionunit",
            "winxp_imageuniqueid",
            "winxp_gpsversion",
            "winxp_gpslatituderef",
            "winxp_gpslatitude",
            "winxp_gpslongituderef",
            "winxp_gpslongitude",
            "winxp_gpsaltituderef",
            "winxp_gpsaltitude",
            "winxp_interoperabilityindex",
            "winxp_interoperabilityversion",
        );
    }
    
    /**
     * Just some little helper function to get the IPTC fields.
     *
     * @return array
     */
    public function getHumanReadableIPTCkey() {
        return array(
            "2#202" => "object_data_preview_data",
            "2#201" => "object_data_preview_file_format_version",
            "2#200" => "object_data_preview_file_format",
            "2#154" => "audio_outcue",
            "2#153" => "audio_duration",
            "2#152" => "audio_sampling_resolution",
            "2#151" => "audio_sampling_rate",
            "2#150" => "audio_type",
            "2#135" => "language_identifier",
            "2#131" => "image_orientation",
            "2#130" => "image_type",
            "2#125" => "rasterized_caption",
            "2#122" => "writer",
            "2#120" => "caption",
            "2#118" => "contact",
            "2#116" => "copyright_notice",
            "2#115" => "source",
            "2#110" => "credit",
            "2#105" => "headline",
            "2#103" => "original_transmission_reference",
            "2#101" => "country_name",
            "2#100" => "country_code",
            "2#095" => "state",
            "2#092" => "sublocation",
            "2#090" => "city",
            "2#085" => "by_line_title",
            "2#080" => "by_line",
            "2#075" => "object_cycle",
            "2#070" => "program_version",
            "2#065" => "originating_program",
            "2#063" => "digital_creation_time",
            "2#062" => "digital_creation_date",
            "2#060" => "creation_time",
            "2#055" => "creation_date",
            "2#050" => "reference_number",
            "2#047" => "reference_date",
            "2#045" => "reference_service",
            "2#042" => "action_advised",
            "2#040" => "special_instruction",
            "2#038" => "expiration_time",
            "2#037" => "expiration_date",
            "2#035" => "release_time",
            "2#030" => "release_date",
            "2#027" => "content_location_name",
            "2#026" => "content_location_code",
            "2#025" => "keywords",
            "2#022" => "fixture_identifier",
            "2#020" => "supplemental_category",
            "2#015" => "category",
            "2#010" => "subject_reference",
            "2#008" => "editorial_update",
            "2#007" => "edit_status",
            "2#005" => "object_name",
            "2#004" => "object_attribute_reference",
            "2#003" => "object_type_reference",
            "2#000" => "record_version",
            "1#090" => "envelope_character_set",
        );
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFieldKeys() {
        $exif_keys_temp = $this->getHumanReadableExifKeys();
        $exif_keys = array();
        foreach ($exif_keys_temp as $value) {
            $exif_keys[$value] = $value;
        }
        $iptc_keys_temp = array_values($this->getHumanReadableIPTCkey());
        $iptc_keys = array();
        foreach ($iptc_keys_temp as $value) {
            $current_value = "iptc_" . $value;
            $iptc_keys[$current_value] = $current_value;
        }
        $fields = array_merge($exif_keys, $iptc_keys);
        ksort($fields);
        return $fields;
    }
    
    /**
     * Convert machine tag values to their human-readable descriptions.
     *
     * @return array
     *   A list of human readable descriptions of meta data values.
     *
     * @see http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/EXIF.html
     * @see http://www.cipa.jp/english/hyoujunka/kikaku/pdf/DC-008-2010_E.pdf
     */
    public function getHumanReadableDescriptions() {
        $machineToHuman = array();
        $machineToHuman['componentsconfiguration'] = array(
            '0' => t('-'),
            '1' => t('Y'),
            '2' => t('Cb'),
            '3' => t('Cr'),
            '4' => t('R'),
            '5' => t('G'),
            '6' => t('B'),
        );
        $machineToHuman['compression'] = array(
            '1' => t('Uncompressed'),
            '2' => t('CCITT 1D'),
            '3' => t('T4/Group 3 Fax'),
            '4' => t('T6/Group 4 Fax'),
            '5' => t('LZW'),
            '6' => t('JPEG (old-style)'),
            '7' => t('JPEG'),
            '8' => t('Adobe Deflate'),
            '9' => t('JBIG B&W'),
            '10' => t('JBIG Color'),
            '99' => t('JPEG'),
            '262' => t('Kodak 262'),
            '32766' => t('Next'),
            '32767' => t('Sony ARW Compressed'),
            '32769' => t('Packed RAW'),
            '32770' => t('Samsung SRW Compressed'),
            '32771' => t('CCIRLEW'),
            '32773' => t('PackBits'),
            '32809' => t('Thunderscan'),
            '32867' => t('Kodak KDC Compressed'),
            '32895' => t('IT8CTPAD'),
            '32896' => t('IT8LW'),
            '32897' => t('IT8MP'),
            '32898' => t('IT8BL'),
            '32908' => t('PixarFilm'),
            '32909' => t('PixarLog'),
            '32946' => t('Deflate'),
            '32947' => t('DCS'),
            '34661' => t('JBIG'),
            '34676' => t('SGILog'),
            '34677' => t('SGILog24'),
            '34712' => t('JPEG 2000'),
            '34713' => t('Nikon NEF Compressed'),
            '34715' => t('JBIG2 TIFF FX'),
            '34718' => t('Microsoft Document Imaging (MDI) Binary Level Codec'),
            '34719' => t('Microsoft Document Imaging (MDI) Progressive Transform Codec'),
            '34720' => t('Microsoft Document Imaging (MDI) Vector'),
            '65000' => t('Kodak DCR Compressed'),
            '65535' => t('Pentax PEF Compressed'),
        );
        $machineToHuman['contrast'] = array(
            '0' => t('Normal'),
            '1' => t('Low'),
            '2' => t('High'),
        );
        $machineToHuman['exposuremode'] = array(
            '0' => t('Auto'),
            '1' => t('Manual'),
            '2' => t('Auto bracket'),
        );
        // The value of 9 is not standard EXIF, but is used by the Canon EOS 7D.
        $machineToHuman['exposureprogram'] = array(
            '0' => t('Not Defined'),
            '1' => t('Manual'),
            '2' => t('Program AE'),
            '3' => t('Aperture-priority AE'),
            '4' => t('Shutter speed priority AE'),
            '5' => t('Creative (Slow speed)'),
            '6' => t('Action (High speed)'),
            '7' => t('Portrait'),
            '8' => t('Landscape'),
            '9' => t('Bulb'),
        );
        $machineToHuman['flash'] = array(
            '0' => t('Flash did not fire'),
            '1' => t('Flash fired'),
            '5' => t('Strobe return light not detected'),
            '7' => t('Strobe return light detected'),
            '9' => t('Flash fired, compulsory flash mode'),
            '13' => t('Flash fired, compulsory flash mode, return light not detected'),
            '15' => t('Flash fired, compulsory flash mode, return light detected'),
            '16' => t('Flash did not fire, compulsory flash mode'),
            '24' => t('Flash did not fire, auto mode'),
            '25' => t('Flash fired, auto mode'),
            '29' => t('Flash fired, auto mode, return light not detected'),
            '31' => t('Flash fired, auto mode, return light detected'),
            '32' => t('No flash function'),
            '65' => t('Flash fired, red-eye reduction mode'),
            '69' => t('Flash fired, red-eye reduction mode, return light not detected'),
            '71' => t('Flash fired, red-eye reduction mode, return light detected'),
            '73' => t('Flash fired, compulsory flash mode, red-eye reduction mode'),
            '77' => t('Flash fired, compulsory flash mode, red-eye reduction mode, return light not detected'),
            '79' => t('Flash fired, compulsory flash mode, red-eye reduction mode, return light detected'),
            '89' => t('Flash fired, auto mode, red-eye reduction mode'),
            '93' => t('Flash fired, auto mode, return light not detected, red-eye reduction mode'),
            '95' => t('Flash fired, auto mode, return light detected, red-eye reduction mode'),
        );
        // Values 1, 4 and 5 are not standard EXIF.
        $machineToHuman['focalplaneresolutionunit'] = array(
            '1' => t('None'),
            '2' => t('inches'),
            '3' => t('cm'),
            '4' => t('mm'),
            '5' => t('um'),
        );
        $machineToHuman['gaincontrol'] = array(
            '0' => t('None'),
            '1' => t('Low gain up'),
            '2' => t('High gain up'),
            '3' => t('Low gain down'),
            '4' => t('High gain down'),
        );
        $machineToHuman['lightsource'] = array(
            '0' => t('Unknown'),
            '1' => t('Daylight'),
            '2' => t('Fluorescent'),
            '3' => t('Tungsten (Incandescent)'),
            '4' => t('Flash'),
            '9' => t('Fine Weather'),
            '10' => t('Cloudy'),
            '11' => t('Shade'),
            '12' => t('Daylight Fluorescent'),
            '13' => t('Day White Fluorescent'),
            '14' => t('Cool White Fluorescent'),
            '15' => t('White Fluorescent'),
            '16' => t('Warm White Fluorescent'),
            '17' => t('Standard Light A'),
            '18' => t('Standard Light B'),
            '19' => t('Standard Light C'),
            '20' => t('D55'),
            '21' => t('D65'),
            '22' => t('D75'),
            '23' => t('D50'),
            '24' => t('ISO Studio Tungsten'),
            '255' => t('Other'),
        );
        $machineToHuman['meteringmode'] = array(
            '0' => t('Unknown'),
            '1' => t('Average'),
            '2' => t('Center-weighted average'),
            '3' => t('Spot'),
            '4' => t('Multi-spot'),
            '5' => t('Multi-segment'),
            '6' => t('Partial'),
            '255' => t('Other'),
        );
        $machineToHuman['orientation'] = array(
            '1' => t('Horizontal (normal)'),
            '2' => t('Mirror horizontal'),
            '3' => t('Rotate 180'),
            '4' => t('Mirror vertical'),
            '5' => t('Mirror horizontal and rotate 270 CW'),
            '6' => t('Rotate 90 CW'),
            '7' => t('Mirror horizontal and rotate 90 CW'),
            '8' => t('Rotate 270 CW'),
        );
        // (the value 1 is not standard EXIF)
        $machineToHuman['resolutionunit'] = array(
            '1' => t('None'),
            '2' => t('inches'),
            '3' => t('cm'),
        );
        $machineToHuman['saturation'] = array(
            '0' => t('Normal'),
            '1' => t('Low'),
            '2' => t('High'),
        );
        $machineToHuman['scenecapturetype'] = array(
            '0' => t('Standard'),
            '1' => t('Landscape'),
            '2' => t('Portrait'),
            '3' => t('Night'),
        );
        // (values 1 and 6 are not standard EXIF)
        $machineToHuman['sensingmethod'] = array(
            '1' => t('Monochrome area'),
            '2' => t('One-chip color area'),
            '3' => t('Two-chip color area'),
            '4' => t('Three-chip color area'),
            '5' => t('Color sequential area'),
            '6' => t('Monochrome linear'),
            '7' => t('Trilinear'),
            '8' => t('Color sequential linear'),
        );
        // (applies to EXIF:ISO tag)
        $machineToHuman['sensitivitytype'] = array(
            '0' => t('Unknown'),
            '1' => t('Standard Output Sensitivity'),
            '2' => t('Recommended Exposure Index'),
            '3' => t('ISO Speed'),
            '4' => t('Standard Output Sensitivity and Recommended Exposure Index'),
            '5' => t('Standard Output Sensitivity and ISO Speed'),
            '6' => t('Recommended Exposure Index and ISO Speed'),
            '7' => t('Standard Output Sensitivity, Recommended Exposure Index and ISO Speed'),
        );
        $machineToHuman['sharpness'] = array(
            '0' => t('Normal'),
            '1' => t('Soft'),
            '2' => t('Hard'),
        );
        $machineToHuman['subjectdistancerange'] = array(
            '0' => t('Unknown'),
            '1' => t('Macro'),
            '2' => t('Close'),
            '3' => t('Distant'),
        );
        $machineToHuman['uncompressed'] = array(
            '0' => t('No'),
            '1' => t('Yes'),
        );
        $machineToHuman['whitebalance'] = array(
            '0' => t('Auto'),
            '1' => t('Manual'),
        );
        return $machineToHuman;
    }

}