How to Implement a PHP JPEG Exif Data Editor to Read and Write JPEG Image Captions in Multiple Languages - PHP JPEG metadata package blog

Today's Open-Source environment offers multiple tools, libraries, and classes to read, translate, and write IPTC-IM automatically.

In this post, I show how you can have your IPTC-IM translated on the fly with only a handful of PHP program lines using existing libraries.

Although multiple freely available libraries exist on the Web (specifically on github.com), I chose to use DeepL's translation API simply because it offers the best translations I have seen.

In nearly all the cases, the translations suggested by DeepL were correct out of the box. The only time I had an issue was when DeepL translated "Cross Country" in the context of cycling into "Langlauf," which means "cross-country skiing."

For the second library, I am biased, as I am using the Metadata class library that I have developed myself in the context of the HOLIDAY photo database project. You can find this class on PHPClasses.org.

You can easily install both libraries using the PHP composer tool with the following commands you can enter in the command line shell console. Alternatively, you may download them from github.com.

composer require deeplcom/deepl-php
composer require diderich/metadata

Next, I make the libraries available to my IPTC-IM translation program using the recommended autoloading mechanism (using the PSR-4 standard).

require_once("vendor/autoload.php");

use \Holiday\Metadata;
use \DeepL\Translator;

To use the translation API from DeepL (or any other provider, like Google or IBM), you need to get an access key ($deep_key).

The process is simple but often requires a credit card to ensure that you do not create multiple accounts to circumvent free usage limitations.

Next, I create an array ($field_ary) to store all the IPTC-IM fields I want to have automatically translated.

For the sake of parameter checking (and the fact that DeepL distinguished between British English and American English), I create an array ($lang_ary) of supported languages.

$deepl_key = ‘xxxxxxxx-xxxx-xxxx-xxxxxxxxxx’;
$fields_ary = [Metadata::CAPTION => 'CAPTION', Metadata::HEADLINE => 'HEADLINE' , Metadata::EVENT => 'EVENT', 
    Metadata::LOCATION => 'LOCATION', Metadata::INSTRUCTIONS => 'INSTRUCTIONS', 
    Metadata::USAGE_TERMS => 'USAGE TERMS', Metadata::KEYWORDS =>  KEYWORDS',      Metadata::SCENES => 'SCENES', 
    Metadata::GENRE => 'GENRE', Metadata::CITY => 'CITY', Metadata::COUNTRY => 'COUNTRY'];
$lang_ary = [‘en’ => ‘en-US’, ‘de’ => ‘de’, ‘fr’ => ‘fr’];

if($argv !== 3 && $argc !== 4) die("$argv[0] src_lang dst_lang src_file [dst_file]\n");
$src_lang = argv[1]; $dst_lan = $argv[2];
$src_file = $argv[3]; $dst_file = $argv[4];
if(!isset($lang_ary[$src_lang])) die("Error: Invalid source language specified '$src_lang'\n");
if(!isset($lang_ary[$dst_lang])) die("Error: Invalid target language specified '$dst_lang'\n");
if(!file_exists($src_file)) die("Error: Image file not found '$src_file'\n");

$metadata = new Metadata();
$translator = new Translator($deepl_key);

$metadata->read($src_file);

Next, I iterate through all the fields I want to translate and translate their content using the DeepL API. Alternatively, you could use Google Translate or IBM Watson translate APIs.

While translating fields, I distinguish between those fields that contain a single text string and those, like keywords, that contain an array of a text string. For reference, I display the translated results on the screen.

foreach($fields_ary as $field_id => $field_name) {
    if($metadata->isset($field_id)) {
        $src_data = $metadata->get($field_id);
        if(is_array($src_data)) {
            $tr_data = array();
            foreach($src_data as $key => $src_text) {
                $tr_data[$key] = $translator->translateText($src_text, $src_lang, $lang_ary[$dst_lang])->text;
            }
            echo "$field_name\n\t".implode(', ', $src_data)."\n\t".implode(', ', $tr_data)."\n";
        }
        else {
            $tr_data = $translator->translateText($src_data, $src_lang, $lang_ary[$dst_lang])->text;
            echo "$field_name\n\t$src_data\n\t$tr_data\n";
        }
        $metadata->set($field_id, empty($tr_data) ? false : $tr_data);
    }
}

$metadata->write($dst_file);

That's it. Now you have a second file containing the translated IPTC-IM. Translating IPTC-IM has never been easier. If needed, you may edit the translated IPTC-IM in your favorite application.

The example below shows all translated fields, as written back to the translated file example.de.jpg.

$ ./trcaption.php en de example.jpg example.de.jpg

CAPTION
    Silver medalists Timea Bacsinszky (left) and Martina Hingis (right) of Switzerland pose on the podium during the ceremony of the women's doubles gold medal match of the tennis tournament on day ten during the 2016 Rio Olympic Games in Rio de Janeiro, Brazil on August 14, 2016
    Die Silbermedaillengewinnerinnen Timea Bacsinszky (links) und Martina Hingis (rechts) aus der Schweiz posieren auf dem Podium während der Zeremonie des Goldmedaillenspiels im Damendoppel des Tennisturniers an Tag zehn der Olympischen Spiele 2016 in Rio de Janeiro, Brasilien, am 14. August 2016

HEADLINE
    Women's Double Tennis Gold Medal Match  During the 2016 Rio Olympic Games
    Tennis-Goldmedaillenmatch im Damendoppel bei den Olympischen Spielen 2016 in Rio

EVENT
    2016 Rio Olympic Games - Tennis
    Olympische Spiele 2016 in Rio - Tennis

INSTRUCTIONS
    * EDITORIAL USE ONLY *
    * NUR FÜR REDAKTIONELLE ZWECKE *

KEYWORDS
    Olympic Games, Tennis, Finals, Women, Sui, Silve Medal, Podium
    Olympische Spiele, Tennis, Endrunde, Frauen, Sui, Silvestermedaille, Podium

SCENES
    Jubilation
    Jubel

CITY
    Rio de Janeiro
    Rio de Janeiro

COUNTRY
    Brazil
    Brasilien

How to Download or Install the PHP JPEG Metadata Package Using PHP Composer Tool