OpenCV CascadeClassifier example for face detection

main.cpp

#include <iostream>
#include <opencv2/opencv.hpp>
#include <stdexcept>

using namespace std;
using namespace cv;

vector<Rect> find_faces(Mat src)
{
	vector<Rect> faces;

	double scale_factor = 1.3;
	int min_neighbor = 5;
	int flags = 0;
	Size min_size = Size(20,20);

	CascadeClassifier cascadeDefault, cascadeAlt, cascadeAltTree, cascadeAlt2, cascadeProfile;
        if (cascadeDefault.load("/usr/local/share/OpenCV/haarcascades/haarcascade_frontalface_default.xml") == true) 
	{
        	cout << "using haarcascade_frontalface_default.xml" << endl;
	        cascadeDefault.detectMultiScale(src, faces, scale_factor, min_neighbor, flags, min_size);
		if(!faces.empty())
			return faces;
        }
	else
	{
                throw runtime_error("cascadeDefault.load() failed...");
	}

	
	if (cascadeAlt.load("/usr/local/share/OpenCV/haarcascades/haarcascade_frontalface_alt.xml") == true) 
	{
        	cout << "using haarcascade_frontalface_alt.xml" << endl;
		cascadeAlt.detectMultiScale(src, faces, scale_factor, min_neighbor, flags, min_size);
                if(!faces.empty())
                        return faces;
        }
	else
	{
		throw runtime_error("cascadeAlt.load() failed...");
	}

	if (cascadeAltTree.load("/usr/local/share/OpenCV/haarcascades/haarcascade_frontalface_alt_tree.xml") == true) 
	{
        	cout << "using haarcascade_frontalface_alt_tree.xml" << endl;
		cascadeAltTree.detectMultiScale(src, faces, scale_factor, min_neighbor, flags, min_size);
                if(!faces.empty())
                        return faces;
        }
	else
	{
		throw runtime_error("cascadeAltTree.load() failed...");
	}

	if (cascadeAlt2.load("/usr/local/share/OpenCV/haarcascades/haarcascade_frontalface_alt2.xml") == true) 
	{
        	cout << "using haarcascade_frontalface_alt2.xml" << endl;
		cascadeAlt2.detectMultiScale(src, faces, scale_factor, min_neighbor, flags, min_size);
                if(!faces.empty())
                        return faces;
        }
	else
	{
		throw runtime_error("cascadeAlt2.load() failed...");
	}

	if (cascadeProfile.load("/usr/local/share/OpenCV/haarcascades/haarcascade_profileface.xml") == true)
        {
                cout << "using haarcascade_profileface.xml" << endl;
                cascadeProfile.detectMultiScale(src, faces, scale_factor, min_neighbor, flags, min_size);
                if(!faces.empty())
                        return faces;
        }
        else
        {
                throw runtime_error("cascadeProfile.load() failed...");
        }

	return faces;
}

int main(int argc, char* argv[])
{
	cv::Mat src_img, gray_img, eq_img, result_img;

	cout << "input argument " << argv[1] << endl;

	src_img = cv::imread(argv[1], CV_LOAD_IMAGE_COLOR);
	if (src_img.data == NULL) {
		cout << "cv::imread() failed...\n" << endl;
		return -1;
	} 

	cvtColor(src_img, gray_img, CV_RGB2GRAY);
	equalizeHist(gray_img, eq_img);
	result_img = src_img.clone();

	vector<Rect> faces = find_faces(eq_img);

	vector<Rect>::const_iterator i;
	for (i = faces.begin(); i != faces.end(); ++i) {
		rectangle(
				result_img,
				Point(i->x, i->y),
				Point(i->x + i->width, i->y + i->height),
				CV_RGB(255, 0, 0),
				2);
	}

	while(true) {
		imshow("result_img", result_img);
		int c = waitKey(0);
		if (c == 27) break;
	}

	return 0; 
}

Makefile

# Makefile
ifeq ($(shell pkg-config --modversion opencv),)
	$(error Package gtkmm-2.4 needed to compile)
endif

CXXFLAGS += `pkg-config --cflags opencv`
LDLIBS += `pkg-config --libs opencv`

BINS = program
program_OBJS = main.o

all: $(BINS)

program: $(program_OBJS)
	$(CXX) $(LDFLAGS) $^ $(LOADLIBES) $(LDLIBS) -o $@

# this part is actually optional, since it's covered by gmake's implicit rules
%.o: %.cc
	$(CXX) -c $(CPPFLAGS) $(CXXFLAGS) $< -o $@