##

    #!/usr/bin/python
    # The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
    #
    # This example program shows how you can use dlib to make an object
    #   detector for things like faces, pedestrians, and any other semi-rigid
    #   object.  In particular, we go though the steps to train the kind of sliding
    #   window object detector first published by Dalal and Triggs in 2005 in the
    #   paper Histograms of Oriented Gradients for Human Detection.
    #
    #
    # COMPILING/INSTALLING THE DLIB PYTHON INTERFACE
    #   You can install dlib using the command:
    #       pip install dlib
    #
    #   Alternatively, if you want to compile dlib yourself then go into the dlib
    #   root folder and run:
    #       python setup.py install
    #   or
    #       python setup.py install --yes USE_AVX_INSTRUCTIONS
    #   if you have a CPU that supports AVX instructions, since this makes some
    #   things run faster.
    #
    #   Compiling dlib should work on any operating system so long as you have
    #   CMake and boost-python installed.  On Ubuntu, this can be done easily by
    #   running the command:
    #       sudo apt-get install libboost-python-dev cmake
    #
    #   Also note that this example requires scikit-image which can be installed
    #   via the command:
    #       pip install scikit-image
    #   Or downloaded from http://scikit-image.org/download.html.

    import os
    import sys
    import glob

    import dlib
    from skimage import io

    # In this example we are going to train a face detector based on the small
    # faces dataset in the examples/faces directory.  This means you need to supply
    # the path to this faces folder as a command line argument so we will know
    # where it is.
    if len(sys.argv) != 2:
        print(
            "Give the path to the examples/faces directory as the argument to this "
            "program. For example, if you are in the python_examples folder then "
            "execute this program by running:\n"
            "    ./train_object_detector.py ../examples/faces")
        exit()
    faces_folder = sys.argv[1]

    # Now let's do the training.  The train_simple_object_detector() function has a
    # bunch of options, all of which come with reasonable default values.  The next
    # few lines goes over some of these options.
    options = dlib.simple_object_detector_training_options()
    # Since faces are left/right symmetric we can tell the trainer to train a
    # symmetric detector.  This helps it get the most value out of the training
    # data.
    options.add_left_right_image_flips = True
    # The trainer is a kind of support vector machine and therefore has the usual
    # SVM C parameter.  In general, a bigger C encourages it to fit the training
    # data better but might lead to overfitting.  You must find the best C value
    # empirically by checking how well the trained detector works on a test set of
    # images you haven't trained on.  Don't just leave the value set at 5.  Try a
    # few different C values and see what works best for your data.
    options.C = 5
    # Tell the code how many CPU cores your computer has for the fastest training.
    options.num_threads = 4
    options.be_verbose = True

    training_xml_path = os.path.join(faces_folder, "training.xml")
    testing_xml_path = os.path.join(faces_folder, "testing.xml")
    # This function does the actual training.  It will save the final detector to
    # detector.svm.  The input is an XML file that lists the images in the training
    # dataset and also contains the positions of the face boxes.  To create your
    # own XML files you can use the imglab tool which can be found in the
    # tools/imglab folder.  It is a simple graphical tool for labeling objects in
    # images with boxes.  To see how to use it read the tools/imglab/README.txt
    # file.  But for this example, we just use the training.xml file included with
    # dlib.
    dlib.train_simple_object_detector(training_xml_path, "detector.svm", options)

    # Now that we have a face detector we can test it.  The first statement tests
    # it on the training data.  It will print(the precision, recall, and then)
    # average precision.
    print("")  # Print blank line to create gap from previous output
    print("Training accuracy: {}".format(
        dlib.test_simple_object_detector(training_xml_path, "detector.svm")))
    # However, to get an idea if it really worked without overfitting we need to
    # run it on images it wasn't trained on.  The next line does this.  Happily, we
    # see that the object detector works perfectly on the testing images.
    print("Testing accuracy: {}".format(
        dlib.test_simple_object_detector(testing_xml_path, "detector.svm")))

    # Now let's use the detector as you would in a normal application.  First we
    # will load it from disk.
    detector = dlib.simple_object_detector("detector.svm")

    # We can look at the HOG filter we learned.  It should look like a face.  Neat!
    win_det = dlib.image_window()
    win_det.set_image(detector)

    # Now let's run the detector over the images in the faces folder and display the
    # results.
    print("Showing detections on the images in the faces folder...")
    win = dlib.image_window()
    for f in glob.glob(os.path.join(faces_folder, "*.jpg")):
        print("Processing file: {}".format(f))
        img = io.imread(f)
        dets = detector(img)
        print("Number of faces detected: {}".format(len(dets)))
        for k, d in enumerate(dets):
            print("Detection {}: Left: {} Top: {} Right: {} Bottom: {}".format(
                k, d.left(), d.top(), d.right(), d.bottom()))

        win.clear_overlay()
        win.set_image(img)
        win.add_overlay(dets)
        dlib.hit_enter_to_continue()

    # Finally, note that you don't have to use the XML based input to
    # train_simple_object_detector().  If you have already loaded your training
    # images and bounding boxes for the objects then you can call it as shown
    # below.

    # You just need to put your images into a list.
    images = [io.imread(faces_folder + '/2008_002506.jpg'),
              io.imread(faces_folder + '/2009_004587.jpg')]
    # Then for each image you make a list of rectangles which give the pixel
    # locations of the edges of the boxes.
    boxes_img1 = ([dlib.rectangle(left=329, top=78, right=437, bottom=186),
                   dlib.rectangle(left=224, top=95, right=314, bottom=185),
                   dlib.rectangle(left=125, top=65, right=214, bottom=155)])
    boxes_img2 = ([dlib.rectangle(left=154, top=46, right=228, bottom=121),
                   dlib.rectangle(left=266, top=280, right=328, bottom=342)])
    # And then you aggregate those lists of boxes into one big list and then call
    # train_simple_object_detector().
    boxes = [boxes_img1, boxes_img2]

    detector2 = dlib.train_simple_object_detector(images, boxes, options)
    # We could save this detector to disk by uncommenting the following.
    #detector2.save('detector2.svm')

    # Now let's look at its HOG filter!
    win_det.set_image(detector2)
    dlib.hit_enter_to_continue()

    # Note that you don't have to use the XML based input to
    # test_simple_object_detector().  If you have already loaded your training
    # images and bounding boxes for the objects then you can call it as shown
    # below.
    print("\nTraining accuracy: {}".format(
        dlib.test_simple_object_detector(images, boxes, detector2)))