Function im_measure_area 

pub unsafe extern "C" fn im_measure_area(
    im: *mut VipsImage,
    left: c_int,
    top: c_int,
    width: c_int,
    height: c_int,
    h: c_int,
    v: c_int,
    sel: *mut c_int,
    nsel: c_int,
    name: *const c_char,
) -> *mut DOUBLEMASK