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231 lines
11 KiB
231 lines
11 KiB
// The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
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/*
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This example shows how to train a CNN based object detector using dlib's
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loss_mmod loss layer. This loss layer implements the Max-Margin Object
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Detection loss as described in the paper:
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Max-Margin Object Detection by Davis E. King (http://arxiv.org/abs/1502.00046).
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This is the same loss used by the popular SVM+HOG object detector in dlib
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(see fhog_object_detector_ex.cpp) except here we replace the HOG features
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with a CNN and train the entire detector end-to-end. This allows us to make
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much more powerful detectors.
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It would be a good idea to become familiar with dlib's DNN tooling before
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reading this example. So you should read dnn_introduction_ex.cpp and
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dnn_introduction2_ex.cpp before reading this example program.
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Just like in the fhog_object_detector_ex.cpp example, we are going to train
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a simple face detector based on the very small training dataset in the
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examples/faces folder. As we will see, even with this small dataset the
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MMOD method is able to make a working face detector. However, for real
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applications you should train with more data for an even better result.
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*/
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#include <iostream>
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#include <dlib/dnn.h>
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#include <dlib/data_io.h>
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#include <dlib/gui_widgets.h>
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using namespace std;
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using namespace dlib;
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// The first thing we do is define our CNN. The CNN is going to be evaluated
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// convolutionally over an entire image pyramid. Think of it like a normal
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// sliding window classifier. This means you need to define a CNN that can look
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// at some part of an image and decide if it is an object of interest. In this
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// example I've defined a CNN with a receptive field of approximately 50x50
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// pixels. This is reasonable for face detection since you can clearly tell if
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// a 50x50 image contains a face. Other applications may benefit from CNNs with
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// different architectures.
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//
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// In this example our CNN begins with 3 downsampling layers. These layers will
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// reduce the size of the image by 8x and output a feature map with
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// 32 dimensions. Then we will pass that through 4 more convolutional layers to
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// get the final output of the network. The last layer has only 1 channel and
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// the values in that last channel are large when the network thinks it has
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// found an object at a particular location.
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// Let's begin the network definition by creating some network blocks.
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// A 5x5 conv layer that does 2x downsampling
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template <long num_filters, typename SUBNET> using con5d = con<num_filters,5,5,2,2,SUBNET>;
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// A 3x3 conv layer that doesn't do any downsampling
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template <long num_filters, typename SUBNET> using con3 = con<num_filters,3,3,1,1,SUBNET>;
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// Now we can define the 8x downsampling block in terms of conv5d blocks. We
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// also use relu and batch normalization in the standard way.
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template <typename SUBNET> using downsampler = relu<bn_con<con5d<32, relu<bn_con<con5d<32, relu<bn_con<con5d<32,SUBNET>>>>>>>>>;
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// The rest of the network will be 3x3 conv layers with batch normalization and
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// relu. So we define the 3x3 block we will use here.
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template <typename SUBNET> using rcon3 = relu<bn_con<con3<32,SUBNET>>>;
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// Finally, we define the entire network. The special input_rgb_image_pyramid
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// layer causes the network to operate over a spatial pyramid, making the detector
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// scale invariant.
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using net_type = loss_mmod<con<1,6,6,1,1,rcon3<rcon3<rcon3<downsampler<input_rgb_image_pyramid<pyramid_down<6>>>>>>>>;
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// ----------------------------------------------------------------------------------------
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int main(int argc, char** argv) try
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{
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// In this example we are going to train a face detector based on the
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// small faces dataset in the examples/faces directory. So the first
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// thing we do is load that dataset. This means you need to supply the
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// path to this faces folder as a command line argument so we will know
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// where it is.
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if (argc != 2)
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{
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cout << "Give the path to the examples/faces directory as the argument to this" << endl;
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cout << "program. For example, if you are in the examples folder then execute " << endl;
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cout << "this program by running: " << endl;
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cout << " ./dnn_mmod_ex faces" << endl;
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cout << endl;
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return 0;
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}
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const std::string faces_directory = argv[1];
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// The faces directory contains a training dataset and a separate
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// testing dataset. The training data consists of 4 images, each
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// annotated with rectangles that bound each human face. The idea is
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// to use this training data to learn to identify human faces in new
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// images.
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//
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// Once you have trained an object detector it is always important to
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// test it on data it wasn't trained on. Therefore, we will also load
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// a separate testing set of 5 images. Once we have a face detector
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// created from the training data we will see how well it works by
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// running it on the testing images.
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//
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// So here we create the variables that will hold our dataset.
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// images_train will hold the 4 training images and face_boxes_train
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// holds the locations of the faces in the training images. So for
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// example, the image images_train[0] has the faces given by the
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// rectangles in face_boxes_train[0].
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std::vector<matrix<rgb_pixel>> images_train, images_test;
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std::vector<std::vector<mmod_rect>> face_boxes_train, face_boxes_test;
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// Now we load the data. These XML files list the images in each dataset
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// and also contain the positions of the face boxes. Obviously you can use
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// any kind of input format you like so long as you store the data into
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// images_train and face_boxes_train. But for convenience dlib comes with
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// tools for creating and loading XML image datasets. Here you see how to
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// load the data. To create the XML files you can use the imglab tool which
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// can be found in the tools/imglab folder. It is a simple graphical tool
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// for labeling objects in images with boxes. To see how to use it read the
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// tools/imglab/README.txt file.
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load_image_dataset(images_train, face_boxes_train, faces_directory+"/training.xml");
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load_image_dataset(images_test, face_boxes_test, faces_directory+"/testing.xml");
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cout << "num training images: " << images_train.size() << endl;
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cout << "num testing images: " << images_test.size() << endl;
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// The MMOD algorithm has some options you can set to control its behavior. However,
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// you can also call the constructor with your training annotations and a "target
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// object size" and it will automatically configure itself in a reasonable way for your
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// problem. Here we are saying that faces are still recognizably faces when they are
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// 40x40 pixels in size. You should generally pick the smallest size where this is
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// true. Based on this information the mmod_options constructor will automatically
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// pick a good sliding window width and height. It will also automatically set the
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// non-max-suppression parameters to something reasonable. For further details see the
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// mmod_options documentation.
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mmod_options options(face_boxes_train, 40,40);
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// The detector will automatically decide to use multiple sliding windows if needed.
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// For the face data, only one is needed however.
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cout << "num detector windows: "<< options.detector_windows.size() << endl;
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for (auto& w : options.detector_windows)
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cout << "detector window width by height: " << w.width << " x " << w.height << endl;
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cout << "overlap NMS IOU thresh: " << options.overlaps_nms.get_iou_thresh() << endl;
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cout << "overlap NMS percent covered thresh: " << options.overlaps_nms.get_percent_covered_thresh() << endl;
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// Now we are ready to create our network and trainer.
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net_type net(options);
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// The MMOD loss requires that the number of filters in the final network layer equal
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// options.detector_windows.size(). So we set that here as well.
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net.subnet().layer_details().set_num_filters(options.detector_windows.size());
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dnn_trainer<net_type> trainer(net);
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trainer.set_learning_rate(0.1);
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trainer.be_verbose();
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trainer.set_synchronization_file("mmod_sync", std::chrono::minutes(5));
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trainer.set_iterations_without_progress_threshold(300);
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// Now let's train the network. We are going to use mini-batches of 150
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// images. The images are random crops from our training set (see
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// random_cropper_ex.cpp for a discussion of the random_cropper).
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std::vector<matrix<rgb_pixel>> mini_batch_samples;
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std::vector<std::vector<mmod_rect>> mini_batch_labels;
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random_cropper cropper;
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cropper.set_chip_dims(200, 200);
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// Usually you want to give the cropper whatever min sizes you passed to the
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// mmod_options constructor, which is what we do here.
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cropper.set_min_object_size(40,40);
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dlib::rand rnd;
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// Run the trainer until the learning rate gets small. This will probably take several
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// hours.
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while(trainer.get_learning_rate() >= 1e-4)
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{
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cropper(150, images_train, face_boxes_train, mini_batch_samples, mini_batch_labels);
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// We can also randomly jitter the colors and that often helps a detector
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// generalize better to new images.
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for (auto&& img : mini_batch_samples)
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disturb_colors(img, rnd);
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trainer.train_one_step(mini_batch_samples, mini_batch_labels);
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}
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// wait for training threads to stop
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trainer.get_net();
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cout << "done training" << endl;
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// Save the network to disk
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net.clean();
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serialize("mmod_network.dat") << net;
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// Now that we have a face detector we can test it. The first statement tests it
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// on the training data. It will print the precision, recall, and then average precision.
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// This statement should indicate that the network works perfectly on the
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// training data.
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cout << "training results: " << test_object_detection_function(net, images_train, face_boxes_train) << endl;
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// However, to get an idea if it really worked without overfitting we need to run
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// it on images it wasn't trained on. The next line does this. Happily,
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// this statement indicates that the detector finds most of the faces in the
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// testing data.
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cout << "testing results: " << test_object_detection_function(net, images_test, face_boxes_test) << endl;
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// If you are running many experiments, it's also useful to log the settings used
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// during the training experiment. This statement will print the settings we used to
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// the screen.
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cout << trainer << cropper << endl;
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// Now lets run the detector on the testing images and look at the outputs.
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image_window win;
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for (auto&& img : images_test)
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{
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pyramid_up(img);
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auto dets = net(img);
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win.clear_overlay();
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win.set_image(img);
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for (auto&& d : dets)
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win.add_overlay(d);
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cin.get();
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}
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return 0;
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// Now that you finished this example, you should read dnn_mmod_train_find_cars_ex.cpp,
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// which is a more advanced example. It discusses many issues surrounding properly
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// setting the MMOD parameters and creating a good training dataset.
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}
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catch(std::exception& e)
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{
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cout << e.what() << endl;
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}
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