FRONTEND_MVC/models/front/Gallery.php

<?php

namespace app\models\front;

use app\forks\galleryManager\GalleryBehavior;
use Yii;

class Gallery extends \app\models\base\Gallery
{
    public function behaviors()
    {
        return [
            'galleryBehavior' => [
                'class' => GalleryBehavior::className(),
                'type' => 'post_gallery',
                'extension' => 'png',
                'directory' => Yii::getAlias('@webroot') . '/images/post_gallery/gallery',
                'url' => Yii::getAlias('@web') . '/images/post_gallery/gallery',
                'versions' => [
                    'small' => function ($img) {
                        /** @var \Imagine\Image\ImageInterface $img */
                        return $img;
                    },
                    'medium' => function ($img) {
                        return $img;
                    },
                ]
            ]
        ];
    }
}