Function decode_v7_rows 

pub fn decode_v7_rows(
    data: &[u8],
    bits: u32,
    width: usize,
    height: usize,
    first_row: usize,
    out: &mut [u16],
    parallel: bool,
) -> Result<()>

Decode rows first_row..first_row + out.len() / width of a format-7 image.