Upvote:2
Please note that you need either a Croatian visa, or a multiple entry Schengen visa to enter Croatia, since they're not a part of the Schengen Area. See this: http://www.mvep.hr/en/consular-information/visas/visa-requirements-overview/
Croatia can't be a point of entry to the Schengen territory.
If you are going to Croatia directly from India, without leaving the airport in Germany, you shouldn't normally clear immigration in Frankfurt. Meaning, your first entry will be in Slovenia.
However, if you will be staying - not just changing planes at the airport - in Frankfurt, you'll clear immigration, and your first entry will be in Germany. If so, if you will have to re-check your baggage in Frankfurt (that depends on your itinerary).