C++ calls Python routines (pybind11)

api.py

# actually src/api.py, but gist demands no subdirectirories
from typing import Tuple, List

import numpy as np


def refine_frame(a: np.ndarray) -> Tuple[List[int], List[List[int]]]:
    print(a.shape)
    return [100, 100, 200, 200], [[[120, 120], [130, 120]]]

main.cpp

#include <opencv2/opencv.hpp>
#include "main.hpp" // everything needed for embedding

using namespace std;
using namespace cv;

FrameInfo* send_frame(int height, int width, const uint8_t* data) {

    py::scoped_interpreter guard{}; // start the interpreter and keep it alive

    py::exec(R"(
        import sys
        sys.path.append('src')
    )");

    py::module_ api_module = py::module_::import("api");

    pybind11::dtype dt("uint8");
    const int shape[3] = {height, width,3};
    py::array py_frame(dt, shape, data);
    py::tuple result = api_module.attr("refine_frame")(py_frame);
    auto b = result[0].cast<std::vector<int>>();
    auto c = result[1].cast<std::vector<std::vector<std::vector<int>>>>();
    return new FrameInfo(b, c);
}



void test_foo() {
    Mat frame;
    VideoCapture cap(0);

    if (!cap.isOpened()) {
        cout << "cannot open camera";
    }

    while (true) {
        cap >> frame;
        imshow("Display window", frame);
        FrameInfo* fi = send_frame(frame.rows, frame.cols, frame.data);
        if ((char) waitKey(1) == (char) 27)
            break;
    }
}


int main() {
    test_foo();
    return EXIT_SUCCESS;
}

main.hpp

#ifndef TEST_APP_CPP_LIB_H
#define TEST_APP_CPP_LIB_H

#include <vector>

struct FrameInfo {
    using first_type = std::vector<int>;
    using second_type = std::vector<std::vector<std::vector<int>>>;

private:
    first_type result1;
    first_type result2;

public:
    FrameInfo(first_type& a, first_type& b): result1(a), result2(b) {};

};

FrameInfo* send_frame(int height, int width, const uint8_t* data);

#endif //TEST_APP_CPP_LIB_H