Human detection

  • 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

We created a project called human_detection with a folder source where we have our example call human_detection.cpp. You can see the complete example here.

In this example we take images from a camera and we use this image to call the RAPP platform and search for humans.

Taking a image from our usb camera uses OpenCV:

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

We created the parameter camera which is our dev0. You will have to check if your camera is the same device and adjust if necessary. In the case that the program doesn't find any devices, it will exit.

If you want to change the resolution of the image from your camera, change the parameters of the camera.

NOTE: The bigger the image is, the more time is needed to process it.


We create an OpenCV window, and then we'll draw rectangles around the humans detected:

cv::namedWindow("Human detection", cv::WINDOW_AUTOSIZE);

The size of the window depends of your camera resolution. At the same time, we initialize our OpenCV matrix where we are going to save the image data from the camera:

cv::Mat frame;

Same as before, we setup the platform ifno and cloud controller:

rapp::cloud::platform info = {"", "9001", "rapp_token"}; 
rapp::cloud::service_controller ctrl(info);

We set the lambda callback, which will iterate over the humans and drawn around them on screen:

auto callback = [&](std::vector<rapp::object::human> humans) { 
    std::cout << "Found: " << humans.size() << " humans" << std::endl; 
    for(auto each_human : humans) {
                      cv::Point(each_human.get_left_x(), each_human.get_left_y()),
                      cv::Point(each_human.get_right_x(), each_human.get_right_x()),
                      1, 8, 0);

This callback shows how many humans have been found and, if there are any it draws a blue rectangle:

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::human_detection>(pic, callback);
    cv::imshow("Human detection", frame);


Add the following lines which use the OpenCV package in cmake:

find_package(OpenCV REQUIRED)
target_link_libraries(human_detection ${RAPP_LIBRARIES}

And modify the names of the executable and the project:

add_executable(human_detection source/human_detection)


  1. Go to your project path (in our case human_detection/)
  2. Build your project:

    mkdir build
    cd build 
    cmake ..
  3. You should now have human_detection in the folder build.
  4. Run your executable: