private function getThemeImageSizes()
    {
        $dataProvider = new DefaultDataProvider();
        $dataProvider->setBaseConfig(['source' => 'tl_image_size']);

        $config = $dataProvider->getEmptyConfig();
        $config->setFields(['id', 'name', 'width', 'height']);
        $config->setSorting(['pid', 'name']);

        $collection = $dataProvider->fetchAll($config);
        if (!$collection->count()) {
            return [];
        }

        $sizes = [];
        foreach ($collection as $model) {
            $sizes[$model->getProperty('id')] = sprintf(
                '%s (%sx%s)',
                $model->getProperty('name'),
                $model->getProperty('width'),
                $model->getProperty('height')
            );
        }

        return $sizes;
    }