Merge pull request #3827 from asmorkalov:as/gapi_migration

Migrate G-API module from main repo to opencv_contrib #3827

Related to https://github.com/opencv/opencv/pull/26469
Required https://github.com/opencv/opencv/pull/26527
CI: https://github.com/opencv/ci-gha-workflow/pull/201

TODO:
- [x]  Python types generator fix
- [x] CI update

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [ ] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/gapi/samples/oak_basic_infer.cpp

@@ -0,0 +1,122 @@
+#include <algorithm>
+#include <iostream>
+#include <sstream>
+
+#include <opencv2/imgproc.hpp>
+#include <opencv2/imgcodecs.hpp>
+#include <opencv2/gapi.hpp>
+#include <opencv2/gapi/core.hpp>
+#include <opencv2/gapi/imgproc.hpp>
+#include <opencv2/gapi/infer.hpp>
+#include <opencv2/gapi/infer/parsers.hpp>
+#include <opencv2/gapi/render.hpp>
+#include <opencv2/gapi/cpu/gcpukernel.hpp>
+#include <opencv2/highgui.hpp>
+
+#include <opencv2/gapi/oak/oak.hpp>
+#include <opencv2/gapi/oak/infer.hpp>
+
+const std::string keys =
+    "{ h help              |             | Print this help message }"
+    "{ detector            |             | Path to compiled .blob face detector model }"
+    "{ duration            | 100         | Number of frames to pull from camera and run inference on }";
+
+namespace custom {
+
+G_API_NET(FaceDetector, <cv::GMat(cv::GFrame)>, "sample.custom.face-detector");
+
+using GDetections = cv::GArray<cv::Rect>;
+using GSize       = cv::GOpaque<cv::Size>;
+using GPrims      = cv::GArray<cv::gapi::wip::draw::Prim>;
+
+G_API_OP(BBoxes, <GPrims(GDetections)>, "sample.custom.b-boxes") {
+    static cv::GArrayDesc outMeta(const cv::GArrayDesc &) {
+        return cv::empty_array_desc();
+    }
+};
+
+GAPI_OCV_KERNEL(OCVBBoxes, BBoxes) {
+    // This kernel converts the rectangles into G-API's
+    // rendering primitives
+    static void run(const std::vector<cv::Rect> &in_face_rcs,
+                          std::vector<cv::gapi::wip::draw::Prim> &out_prims) {
+        out_prims.clear();
+        const auto cvt = [](const cv::Rect &rc, const cv::Scalar &clr) {
+            return cv::gapi::wip::draw::Rect(rc, clr, 2);
+        };
+        for (auto &&rc : in_face_rcs) {
+            out_prims.emplace_back(cvt(rc, CV_RGB(0,255,0))); // green
+        }
+    }
+};
+
+} // namespace custom
+
+int main(int argc, char *argv[]) {
+    cv::CommandLineParser cmd(argc, argv, keys);
+    if (cmd.has("help")) {
+        cmd.printMessage();
+        return 0;
+    }
+
+    const auto det_name = cmd.get<std::string>("detector");
+    const auto duration = cmd.get<int>("duration");
+
+    if (det_name.empty()) {
+        std::cerr << "FATAL: path to detection model is not provided for the sample."
+                  << "Please specify it with --detector options."
+                  << std::endl;
+        return 1;
+    }
+
+    // Prepare G-API kernels and networks packages:
+    auto detector = cv::gapi::oak::Params<custom::FaceDetector>(det_name);
+    auto networks = cv::gapi::networks(detector);
+
+    auto kernels = cv::gapi::combine(
+        cv::gapi::kernels<custom::OCVBBoxes>(),
+        cv::gapi::oak::kernels());
+
+    auto args = cv::compile_args(kernels, networks);
+
+    // Initialize graph structure
+    cv::GFrame in;
+    cv::GFrame copy = cv::gapi::oak::copy(in); // NV12 transfered to host + passthrough copy for infer
+    cv::GOpaque<cv::Size> sz = cv::gapi::streaming::size(copy);
+
+    // infer is not affected by the actual copy here
+    cv::GMat blob = cv::gapi::infer<custom::FaceDetector>(copy);
+    // FIXME: OAK infer detects faces slightly out of frame bounds
+    cv::GArray<cv::Rect> rcs = cv::gapi::parseSSD(blob, sz, 0.5f, true, false);
+    auto rendered = cv::gapi::wip::draw::renderFrame(copy, custom::BBoxes::on(rcs));
+    // on-the-fly conversion NV12->BGR
+    cv::GMat out = cv::gapi::streaming::BGR(rendered);
+
+    auto pipeline  = cv::GComputation(cv::GIn(in), cv::GOut(out, rcs))
+        .compileStreaming(std::move(args));
+
+    // Graph execution
+    pipeline.setSource(cv::gapi::wip::make_src<cv::gapi::oak::ColorCamera>());
+    pipeline.start();
+
+    cv::Mat out_mat;
+    std::vector<cv::Rect> out_dets;
+    int frames = 0;
+    while (pipeline.pull(cv::gout(out_mat, out_dets))) {
+        std::string name = "oak_infer_frame_" + std::to_string(frames) + ".png";
+
+        cv::imwrite(name, out_mat);
+
+        if (!out_dets.empty()) {
+            std::cout << "Got " << out_dets.size() << " detections on frame #" << frames << std::endl;
+        }
+
+        ++frames;
+        if (frames == duration) {
+            pipeline.stop();
+            break;
+        }
+    }
+    std::cout << "Pipeline finished. Processed " << frames << " frames" << std::endl;
+    return 0;
+}