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+// The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
+/*
+
+ This example program shows how to find frontal human faces in an image. In
+ particular, this program shows how you can take a list of images from the
+ command line and display each on the screen with red boxes overlaid on each
+ human face.
+
+ The examples/faces folder contains some jpg images of people. You can run
+ this program on them and see the detections by executing the following command:
+ ./face_detection_ex faces/*.jpg
+
+
+ This face detector is made using the now classic Histogram of Oriented
+ Gradients (HOG) feature combined with a linear classifier, an image pyramid,
+ and sliding window detection scheme. This type of object detector is fairly
+ general and capable of detecting many types of semi-rigid objects in
+ addition to human faces. Therefore, if you are interested in making your
+ own object detectors then read the fhog_object_detector_ex.cpp example
+ program. It shows how to use the machine learning tools which were used to
+ create dlib's face detector.
+
+
+ Finally, note that the face detector is fastest when compiled with at least
+ SSE2 instructions enabled. So if you are using a PC with an Intel or AMD
+ chip then you should enable at least SSE2 instructions. If you are using
+ cmake to compile this program you can enable them by using one of the
+ following commands when you create the build project:
+ cmake path_to_dlib_root/examples -DUSE_SSE2_INSTRUCTIONS=ON
+ cmake path_to_dlib_root/examples -DUSE_SSE4_INSTRUCTIONS=ON
+ cmake path_to_dlib_root/examples -DUSE_AVX_INSTRUCTIONS=ON
+ This will set the appropriate compiler options for GCC, clang, Visual
+ Studio, or the Intel compiler. If you are using another compiler then you
+ need to consult your compiler's manual to determine how to enable these
+ instructions. Note that AVX is the fastest but requires a CPU from at least
+ 2011. SSE4 is the next fastest and is supported by most current machines.
+*/
+
+
+#include <dlib/image_processing/frontal_face_detector.h>
+#include <dlib/gui_widgets.h>
+#include <dlib/image_io.h>
+#include <iostream>
+
+using namespace dlib;
+using namespace std;
+
+// ----------------------------------------------------------------------------------------
+
+int main(int argc, char** argv)
+{
+ try
+ {
+ if (argc == 1)
+ {
+ cout << "Give some image files as arguments to this program." << endl;
+ return 0;
+ }
+
+ frontal_face_detector detector = get_frontal_face_detector();
+ image_window win;
+
+ // Loop over all the images provided on the command line.
+ for (int i = 1; i < argc; ++i)
+ {
+ cout << "processing image " << argv[i] << endl;
+ array2d<unsigned char> img;
+ load_image(img, argv[i]);
+ // Make the image bigger by a factor of two. This is useful since
+ // the face detector looks for faces that are about 80 by 80 pixels
+ // or larger. Therefore, if you want to find faces that are smaller
+ // than that then you need to upsample the image as we do here by
+ // calling pyramid_up(). So this will allow it to detect faces that
+ // are at least 40 by 40 pixels in size. We could call pyramid_up()
+ // again to find even smaller faces, but note that every time we
+ // upsample the image we make the detector run slower since it must
+ // process a larger image.
+ pyramid_up(img);
+
+ // Now tell the face detector to give us a list of bounding boxes
+ // around all the faces it can find in the image.
+ std::vector<rectangle> dets = detector(img);
+
+ cout << "Number of faces detected: " << dets.size() << endl;
+ // Now we show the image on the screen and the face detections as
+ // red overlay boxes.
+ win.clear_overlay();
+ win.set_image(img);
+ win.add_overlay(dets, rgb_pixel(255,0,0));
+
+ cout << "Hit enter to process the next image..." << endl;
+ cin.get();
+ }
+ }
+ catch (exception& e)
+ {
+ cout << "\nexception thrown!" << endl;
+ cout << e.what() << endl;
+ }
+}
+
+// ----------------------------------------------------------------------------------------
+