Yes, users can access images, full texts and metadata via an API (Application Programming Interface). The API of the German Digital Library is documented with an OpenAPI specification.
You can find an interactive representation here. If you open the tab for /search/index/{indexname}/{requesthandler}, you will see the two Solr search indices „newspaper“ and „newspaper-issues“. The „newspaper“ search index provides information on the newspapers in the newspaper portal, while the „newspaper-issues“ search index provides information on the issues available in the newspaper portal. You can run queries directly on this website and view the results. The Solr schemas for the field names of the search indices are also linked in the API documentation. The small library ddbapi which is available on PyPI (source code) provides a wrapper for using the API with the programming language Python.