feat: make feature image separate

only for the post without feature image in the home page
issue #237

inc/api.php

@@ -120,7 +120,12 @@ function cover_gallery() {
  * @rest api接口路径：https://sakura.2heng.xin/wp-json/sakura/v1/image/feature
  */
 function feature_gallery() {
-    return cover_gallery();
+    $imgurl = Images::feature_gallery();
+    $data = array('feature image');
+    $response = new WP_REST_Response($data);
+    $response->set_status(302);
+    $response->header('Location', $imgurl);
+    return $response;
 }
 
 /*

inc/classes/Images.php

@@ -162,4 +162,13 @@ class Images
         }
         return $imgurl;
     }
+
+    public static function feature_gallery() {
+        if (akina_option('post_cover_options') == "type_2") {
+            $imgurl = akina_option('post_cover');
+        } else {
+            $imgurl = self::cover_gallery();
+        }
+        return $imgurl;
+    }
 }

options.php

@@ -234,6 +234,25 @@ function optionsframework_options()
             'imageflow' => __('Graphic', 'sakura'), /*图文*/
         ));
 
+    $options[] = array(
+        'name' => __('Cover manifest', 'sakura'), /*首页文章特色图选项*/
+        'desc' => __('Select how to call the post featue image, only for the post without feature image', 'sakura'), /*选择文章特色图的调用方式，只对没有设置特色图像的文章生效*/
+        'id' => 'post_cover_options',
+        'std' => "type_1",
+        'type' => "select",
+        'options' => array(
+            'type_1' => __('same as the cover of the first screen (default)', 'sakura'), /*跟随第一屏封面图*/
+            'type_2' => __('custom api (advanced)', 'sakura'), /*外部随机图API*/
+        )
+    );
+
+    $options[] = array(
+        'name' => __('Cover images url', 'sakura'), /*图片库url*/
+        'desc' => __('Fill in the custom image api url.', 'sakura'),
+        'id' => 'post_cover',
+        'std' => '',
+        'type' => 'text');
+
     $options[] = array(
         'name' => __('Home article feature images (only valid for standard mode)', 'sakura'), /*首页文章特色图（仅对标准风格生效）*/
         'id' => 'list_type',