Update media type detection with GD driver

The updated method tries to use the more reliable finfo methods to
detect mime type when they are available. When finfo is not installed
getimagesize() or getimagesizefromstring() is used as a fallback.

Author: olivervogel

src/Drivers/Gd/Decoders/AbstractDecoder.php

@@ -21,6 +21,17 @@ abstract class AbstractDecoder extends SpecializableDecoder implements Specializ
      */
     protected function getMediaTypeByFilePath(string $filepath): MediaType
     {
+        if (function_exists('finfo_file') && function_exists('finfo_open')) {
+            $mediaType = finfo_file(finfo_open(FILEINFO_MIME_TYPE), $filepath);
+            if (is_string($mediaType)) {
+                try {
+                    return MediaType::from($mediaType);
+                } catch (ValueError) {
+                    throw new NotSupportedException('Unsupported media type (MIME) ' . $mediaType . '.');
+                }
+            }
+        }
+
         $info = @getimagesize($filepath);
 
         if (!is_array($info)) {
@@ -42,6 +53,17 @@ protected function getMediaTypeByFilePath(string $filepath): MediaType
      */
     protected function getMediaTypeByBinary(string $data): MediaType
     {
+        if (function_exists('finfo_buffer') && function_exists('finfo_open')) {
+            $mediaType = finfo_buffer(finfo_open(FILEINFO_MIME_TYPE), $data);
+            if (is_string($mediaType)) {
+                try {
+                    return MediaType::from($mediaType);
+                } catch (ValueError) {
+                    throw new NotSupportedException('Unsupported media type (MIME) ' . $mediaType . '.');
+                }
+            }
+        }
+
         $info = @getimagesizefromstring($data);
 
         if (!is_array($info)) {