Allow to fetch custom meta fields for uploaded images.

src/Field/Image.php

@@ -53,6 +53,11 @@ class Image extends BasicField implements FieldInterface
      */
     protected $loadFromPost = false;
 
+    /**
+     * @var Post
+     */
+    protected $attachment;
+
     /**
      * @param string $field
      */
@@ -87,6 +92,7 @@ protected function fillFields(Post $attachment)
         $this->mime_type = $attachment->post_mime_type;
         $this->url = $attachment->guid;
         $this->description = $attachment->post_excerpt;
+        $this->attachment = $attachment;
     }
 
     /**
@@ -164,4 +170,28 @@ protected function fillMetadataFields(array $imageData)
         $this->height = $imageData['height'];
         $this->sizes = $imageData['sizes'];
     }
+
+    /**
+     * @param string|array      comma seperated string or an array
+     *
+     * @return string|array     string if only one meta key was received as input, otherwise an array with the values of all meta keys received as input
+     */
+    public function fetchCustomMetadataValues($metaKeys)
+    {
+        if (!is_array($metaKeys)) {
+            $metaKeys = explode(',', $metaKeys);
+        }
+
+        $customMetaValues = [];
+
+        foreach ($metaKeys as $metaKey) {
+            $customMetaValues[] = $this->attachment->meta->{trim($metaKey)};
+        }
+
+        if (count($customMetaValues) === 1) {
+            return $customMetaValues[0];
+        }
+
+        return $customMetaValues;
+    }
 }

tests/ContentFieldsTest.php

@@ -89,4 +89,25 @@ public function testGalleryFieldValue()
         $this->assertEquals(1920, $image->width);
         $this->assertEquals(1080, $image->height);
     }
+
+    public function testImageCustomMetadataValues($value='')
+    {
+        $image = new Image($this->post);
+        $image->process('fake_image');
+
+        $this->assertCount(
+            4,
+            $image->fetchCustomMetadataValues(
+                '_gallery_link_url,
+                _gallery_link_target,
+                _gallery_link_preserve_click,
+                _gallery_link_additional_css_classes')
+        );
+        $this->assertTrue(is_string($image->fetchCustomMetadataValues('_gallery_link_url')));
+
+        $this->assertEquals('www.example.com', $image->fetchCustomMetadataValues('_gallery_link_url'));
+        $this->assertEquals('_blank', $image->fetchCustomMetadataValues('_gallery_link_target'));
+        $this->assertEquals('remove', $image->fetchCustomMetadataValues('_gallery_link_preserve_click'));
+        $this->assertEquals('underlined', $image->fetchCustomMetadataValues('_gallery_link_additional_css_classes'));
+    }
 }