Function rs_Convert16To8Plane 

pub unsafe extern "C" fn rs_Convert16To8Plane(
    src_y: *const u16,
    src_stride_y: c_int,
    dst_y: *mut u8,
    dst_stride_y: c_int,
    scale: c_int,
    width: c_int,
    height: c_int,
)