How to caculate ORB match rate of two image

Currently I need to get the match rate of two image, and try to get ORB descriptor’s key point size.It seems no method to get the size.Any ideas?
Thanks in advance.

Looks like the object type wasn’t built out. Um, if you save the descriptor to disk then you can read it back in as a binary file in the mean time to get this info

Here’s some code showing the format:

First 4 bytes are the type. Second 4 bytes are the number of keypoints (size).

Thanks, I have change the py_image.c and it is work.
The code is below:

mp_obj_t py_kp_size(mp_obj_t self_in)
	return mp_obj_new_int(array_length(((py_kp_obj_t *)self_in)->kpts));

STATIC MP_DEFINE_CONST_FUN_OBJ_1(py_kp_size_obj, py_kp_size);
STATIC const mp_rom_map_elem_t py_kp_locals_dict_table[] = {
    { MP_ROM_QSTR(MP_QSTR_size), MP_ROM_PTR(&py_kp_size_obj) },

STATIC MP_DEFINE_CONST_DICT(py_kp_locals_dict, py_kp_locals_dict_table);
static void py_kp_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind)
    py_kp_obj_t *self = self_in;
    mp_printf(print, "size:%d threshold:%d normalized:%d", array_length(self->kpts), self->threshold, self->normalized);

static const mp_obj_type_t py_kp_type = {
    { &mp_type_type },
    .name  = MP_QSTR_kp_desc,
    .print = py_kp_print,
    .locals_dict = (mp_obj_t) &py_kp_locals_dict,


I’ll make a class for the match object and a class for the keypoints descriptor in the next release, thanks for bringing that up, also if you have any feedback/question on ORB/Keypoints please let me know. Thanks!