Thranduil and the Mirkwood elves?

[Legolas]

Galadriel, while only 1/4 Noldorin by blood, is considered a Noldorin elf. Elrond is of a very mixed heritage - Vanyar (Indis, Elenwe), Teleri/Sindar (Thingol), Noldor (Finwe,Anaire), Human (Beren, Tuor), and Ainur (Melian). Legolas and his father Thranduil are Sindar from Doriath (as is Celeborn). Most of the elves in Mirkwood are presumed to be Silvan folk. There would be some Nandorin blood there perhaps, and more Sindar migrated from Beleriand, mixing with the Silvan. There's an appendix to 'The History of Galadriel and Celeborn' in Unfinished Tales about the Sindarin princes establishing kingdoms among the Silvan - explores the possible origins of Thranduil's establishment and his ancestry (Oropher).

And Galadriel's pure silvan elf, and she looks like the elves from Mirkwood do, and the sindar look different from the silvans.

What's this based on? The movies?