I do have a filename from wikimedia commons and I want to access the thumbnail-image directly.
Example: Tour_Eiffel_Wikimedia_Commons.jpg
I found a way to get json-data containing the url to the thumbnail I want:
https://en.wikipedia.org/w/api.php?action=query&titles=Image:Tour_Eiffel_Wikimedia_Commons.jpg&prop=imageinfo&iiprop=url&iiurlwidth=200
but I don't want another request. Is there a way to access the thumbnail directly?
If you're okay to rely on the fact the current way of building the URL won't change in the future (which is not guaranteed), then you can do it.
The URL looks like this:
https://upload.wikimedia.org/wikipedia/commons/thumb/a/a8/Tour_Eiffel_Wikimedia_Commons.jpg/200px-Tour_Eiffel_Wikimedia_Commons.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb
Tour_Eiffel_Wikimedia_Commons.jpg
is a85d416ee427dfaee44b9248229a9cdd
, so we get /a
./a8
./Tour_Eiffel_Wikimedia_Commons.jpg
/200px-Tour_Eiffel_Wikimedia_Commons.jpg