[BUGFIX] Normalize EXIF flash value (#42)

Some manufacturers do not comply with the EXIF specifications
and store a description of the behaviour of the flash instead
of the correct integer value representing that behaviour.

The Flash utility processor takes care of normalizing an
invalid textual representation into its corresponding correct
value.

Resolves: #39

Classes/Utility/Flash.php

@@ -0,0 +1,82 @@
+<?php
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace Causal\Extractor\Utility;
+
+use TYPO3\CMS\Core\Utility\MathUtility;
+
+/**
+ * Flash utility class.
+ *
+ * @author      Xavier Perseguers <xavier@causal.ch>
+ * @license     http://www.gnu.org/copyleft/gpl.html
+ */
+class Flash
+{
+    /**
+     * Normalize an EXIF flash value to its integer representation
+     *
+     * This is needed because some manufacturers store the description
+     * of how the flash behaved instead of the integer value as given
+     * in the specifications.
+     *
+     * @param string|null $str
+     * @return int|null
+     */
+    public static function normalize(?string $str = null, ?string $reference = null): ?int
+    {
+        if ($str === null) {
+            return null;
+        }
+
+        if (MathUtility::canBeInterpretedAsInteger($str)) {
+            return (int)$str;
+        }
+
+        // See https://www.exiftool.org/TagNames/EXIF.html#Flash
+        $mapping = [
+            0x0 => 'No Flash',
+            0x1 => 'Fired',
+            0x5 => 'Fired, Return not detected',
+            0x7 => 'Fired, Return detected',
+            0x8 => 'On, Did not fire',
+            0x9 => 'On, Fired',
+            0xd => 'On, Return not detected',
+            0xf => 'On, Return detected',
+            0x10 => 'Off, Did not fire',
+            0x14 => 'Off, Did not fire, Return not detected',
+            0x18 => 'Auto, Did not fire',
+            0x19 => 'Auto, Fired',
+            0x1d => 'Auto, Fired, Return not detected',
+            0x1f => 'Auto, Fired, Return detected',
+            0x20 => 'No flash function',
+            0x30 => 'Off, No flash function',
+            0x41 => 'Fired, Red-eye reduction',
+            0x45 => 'Fired, Red-eye reduction, Return not detected',
+            0x47 => 'Fired, Red-eye reduction, Return detected',
+            0x49 => 'On, Red-eye reduction',
+            0x4d => 'On, Red-eye reduction, Return not detected',
+            0x4f => 'On, Red-eye reduction, Return detected',
+            0x50 => 'Off, Red-eye reduction',
+            0x58 => 'Auto, Did not fire, Red-eye reduction',
+            0x59 => 'Auto, Fired, Red-eye reduction',
+            0x5d => 'Auto, Fired, Red-eye reduction, Return not detected',
+            0x5f => 'Auto, Fired, Red-eye reduction, Return detected',
+        ];
+
+        $key = array_search($str, $mapping);
+
+        return $key !== false ? $key : 0;
+    }
+}

Configuration/Services/ExifTool/default.json

@@ -167,7 +167,7 @@
   },
   {
 	"FAL": "flash",
-	"DATA": "Flash"
+	"DATA": "Flash->Causal\\Extractor\\Utility\\Flash::normalize"
   },
   {
     "FAL": "__categories__",

Configuration/Services/Php/default.json

@@ -167,6 +167,6 @@
   },
   {
     "FAL": "flash",
-    "DATA": "Flash"
+    "DATA": "Flash->Causal\\Extractor\\Utility\\Flash::normalize"
   }
 ]

Configuration/Services/Tika/default.json

@@ -167,6 +167,6 @@
   },
   {
     "FAL": "flash",
-    "DATA": "exif:Flash"
+    "DATA": "exif:Flash->Causal\\Extractor\\Utility\\Flash::normalize"
   }
 ]