Function orient_plane 

fn orient_plane(
    src: &[u8],
    stride: usize,
    w: usize,
    h: usize,
    o: Orientation,
    dst: &mut [u8],
)

Rotate one plane clockwise into a tightly packed destination (whose width is h for odd turn counts), mirroring each destination row for hflip.

Half turns keep rows as rows and are copied as such. A quarter turn gathers a source column per destination row, so it is taken in tiles: a whole-row pass touches every source row once per output row and spills the cache on any frame that does not fit in it.