Object recognition

  • This tutorial assumes that RAPP API and OpenCV are installed and built
  • This tutorial uses the 0.7.0 version of the C++ API

We are going to create a project using OpenCV, RAPP API and CMake. Using CMake requires you to configure your CMakeLists.txt in the root of your RAPP project. The structure is the following:


Source code

The source is inside the folder source where we have the example object_recognition.cpp. You can see the complete example here.

In this example we are taking images from a camera and we are using them to call the RAPP platform and detect objects. Object detection returns the highest clasification class of the object found in the image.

For taking a image from our usb camera we have to use OpenCV:

cv::VideoCapture camera(0); 
if(!camera.isOpened()) { 
    std::cout << "Failed to connect to the camera" << std::endl;
    return -1;

We create the variable camera which is at dev0. You will have to check if your camera is the same device and change it if needed.

If you want to change the resolution of the image from your camera, change the parameters of the camera. You have to remember that the bigger the image is, the more time is needed to process it.


The callback that receives the cloud reply

auto callback = [&](std::string object) { 
        if (object.empty()) {
            std::cout << "No object found" << std::endl;
        else {
            std::cout << "Found " << object << std::endl;
            cv::putText(frame, objects, cv::Point(50,50), cv::FONT_HERSHEY_PLAIN, 2, cv::Scalar(0, 0, 255), 2);

This callback shows what object has been found and, if there is any, it draws the description of the object in the window.

if (elapsed > 500) {
    camera >> frame;
    std::vector<int> param = {{ CV_IMWRITE_PNG_COMPRESSION, 3 }};
    cv::vector<uchar> buf;
    cv::imencode(".png", frame, buf, param);
    std::vector<rapp::types::byte> bytes(buf.begin(), buf.end());
    auto pic = rapp::object::picture(bytes);
    before = now;
    ctrl.make_call<rapp::cloud::object_recognition>(pic, callback);
    cv::imshow("Object recognition", frame);

Building the example

  • Go to your project path (in our case object_recognition/)
  • Build the example:
    mkdir build
    cd build 
    cmake ..
  • Run the executable