// The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
    This example shows how to run a CNN based face detector using dlib.  The
    example loads a pretrained model and uses it to find faces in images.  The
    CNN model is much more accurate than the HOG based model shown in the
    face_detection_ex.cpp example, but takes much more computational power to
    run, and is meant to be executed on a GPU to attain reasonable speed.  For
    example, on a NVIDIA Titan X GPU, this example program processes images at
    about the same speed as face_detection_ex.cpp.

    Also, users who are just learning about dlib's deep learning API should read
    the dnn_introduction_ex.cpp and dnn_introduction2_ex.cpp examples to learn
    how the API works.  For an introduction to the object detection method you
    should read dnn_mmod_ex.cpp

        Finally, users interested in how the face detector was trained should
        read the dnn_mmod_ex.cpp example program.  It should be noted that the
        face detector used in this example uses a bigger training dataset and
        larger CNN architecture than what is shown in dnn_mmod_ex.cpp, but
        otherwise training is the same.  If you compare the net_type statements
        in this file and dnn_mmod_ex.cpp you will see that they are very similar
        except that the number of parameters has been increased.

        Additionally, the following training parameters were different during
        training: The following lines in dnn_mmod_ex.cpp were changed from
            mmod_options options(face_boxes_train, 40*40);
        to the following when training the model used in this example:
            mmod_options options(face_boxes_train, 80*80);

        Also, the random_cropper was left at its default settings,  So we didn't
        call these functions:
            cropper.set_chip_dims(200, 200);

        The training data used to create the model is also available at 

#include <iostream>
#include <dlib/dnn.h>
#include <dlib/data_io.h>
#include <dlib/image_processing.h>
#include <dlib/gui_widgets.h>

using namespace std;
using namespace dlib;

// ----------------------------------------------------------------------------------------

template <long num_filters, typename SUBNET> using con5d = con<num_filters,5,5,2,2,SUBNET>;
template <long num_filters, typename SUBNET> using con5  = con<num_filters,5,5,1,1,SUBNET>;

template <typename SUBNET> using downsampler  = relu<affine<con5d<32, relu<affine<con5d<32, relu<affine<con5d<16,SUBNET>>>>>>>>>;
template <typename SUBNET> using rcon5  = relu<affine<con5<45,SUBNET>>>;

using net_type = loss_mmod<con<1,9,9,1,1,rcon5<rcon5<rcon5<downsampler<input_rgb_image_pyramid<pyramid_down<6>>>>>>>>;

// ----------------------------------------------------------------------------------------

int main(int argc, char** argv) try
    if (argc == 1)
        cout << "Call this program like this:" << endl;
        cout << "./dnn_mmod_face_detection_ex mmod_human_face_detector.dat faces/*.jpg" << endl;
        cout << "\nYou can get the mmod_human_face_detector.dat file from:\n";
        cout << "http://dlib.net/files/mmod_human_face_detector.dat.bz2" << endl;
        return 0;

    net_type net;
    deserialize(argv[1]) >> net;  

    image_window win;
    for (int i = 2; i < argc; ++i)
        matrix<rgb_pixel> img;
        load_image(img, argv[i]);

        // Upsampling the image will allow us to detect smaller faces but will cause the
        // program to use more RAM and run longer.
        while(img.size() < 1800*1800)

        // Note that you can process a bunch of images in a std::vector at once and it runs
        // much faster, since this will form mini-batches of images and therefore get
        // better parallelism out of your GPU hardware.  However, all the images must be
        // the same size.  To avoid this requirement on images being the same size we
        // process them individually in this example.
        auto dets = net(img);
        for (auto&& d : dets)

        cout << "Hit enter to process the next image." << endl;
catch(std::exception& e)
    cout << e.what() << endl;