Where does Serviio store image thumbnails?

As it is simply too slow to have Serviio serve images via DLNA due to the thumbnail issue, I have decided to stop using it for images.

Now, I want to delete all the thumbnails that Serviio already has created. Where are these stored? I can't seem to find them.

Thanks

Martin

[zip]

they re in the library database - you won't be able to delete them manually