public function getCreateThumbnail()
    {
        if (!$this->isImage) {
            return false;
        }

        $tinyCrop = Yii::$app->storage->getFilterId(TinyCrop::identifier());
        foreach ($this->images as $image) {
            if ($image->filter_id == $tinyCrop) {
                return ['source' => $image->source];
            }
        }

        // create the thumbnail on the fly if not existing
        $image = Yii::$app->storage->createImage($this->id, $tinyCrop);
        if ($image) {
            return ['source' => $image->source];
        }
    }