a 32 by 32 or a 64 by 64 then they unroll it which simply means they go through the image like this and make a sequence out of it because their models are naturally made for text sequences they simply put the image into a text sequence they further simplify this by reducing the three colour channels to a single one so they have their own color representation and basically yeah they reduce the three colour channels to one channel that simply indexes the color in their color representation and they say still pretty good it's pretty faithful