#include <stdio.h> // For printf()

#include <cv.h>  // Main OpenCV library.

#include <highgui.h> // OpenCV functions for files and graphical windows.

using namespace std;

using namespace cv;

// Initialize a sub funcion using after main

CvRect detectFaceInImage( IplImage *inputImg, CvHaarClassifierCascade* cascade);

int main(int argc, char* argv[])

{

    CvPoint pt1, pt2;    // For draw rectangle

    // Check the input is correct when call executable file

    if (argc != 2)

    {

         printf("Usage: faceDetector.exe <imagename>\n");

         exit(-1);

    }

    char * imgName = argv[1];    // Copy the second input as the image name

    // Load image

    IplImage* inputImg = cvLoadImage(imgName, CV_LOAD_IMAGE_UNCHANGED);

    if (!inputImg) {

         printf("Error: Could not open the image file! \n");

         exit(-1);

    }

    // Haar Cascade file, used for Face Detection.

    // Note: you could change this directory as your installed OpenCV2.1 location

    char *faceCascadeFilename = "C:/OpenCV2.1/data/haarcascades/haarcascade_frontalface_alt.xml";

    // Load the HaarCascade classifier for face detection.

    CvHaarClassifierCascade* faceCascade;

    faceCascade = (CvHaarClassifierCascade*)cvLoad(faceCascadeFilename, 0, 0, 0);

    if( !faceCascade ) {

         printf("Couldnt load Face detector '%s'\n", faceCascadeFilename);

         exit(-1);

    }

    // Perform face detection on the input image, using the given Haar classifier

    CvRect faceRect = detectFaceInImage(inputImg, faceCascade);

    // Make sure a valid face was detected then draw the rect location.

    if (faceRect.width > 0)

    {

         printf("Detected a face at (%d,%d)!\n", faceRect.x, faceRect.y);

         // Get the pointer of the face rectangle

         pt1.x = faceRect.x;

         pt2.x = faceRect.x + faceRect.width;

         pt1.y = faceRect.y;

          pt2.y = faceRect.y + faceRect.height;

         // Draw the rectangle in the input image

          cvRectangle( inputImg, pt1, pt2, CV_RGB(255,0,0), 2, 8, 0 );

         // Show the detected face image on the screen.

         cvNamedWindow("Detected face", CV_WINDOW_AUTOSIZE);

         // Show the image in the window named "Detected face", you could change as you like

         cvShowImage( "Detected face", inputImg );

         // Wait for the user to press something on the graphical window.

         // Note: cvWaitKey() is needed for time to draw on the screen.

         cvWaitKey(0);

         // Free the resources.

         cvDestroyWindow("Detected face");

         cvReleaseImage( &inputImg );

     }

    // Free the Face Detector resources when the program is finished

    cvReleaseHaarClassifierCascade( &faceCascade );

    return 0;

}

// Perform face detection on the input image, using the given Haar Cascade.

// Returns a rectangle for the detected region in the given image.

CvRect detectFaceInImage(IplImage *inputImg, CvHaarClassifierCascade* cascade)

{

    // Smallest face size.

    CvSize minFeatureSize = cvSize(20, 20);

    // Only search for 1 face.

    int flags = CV_HAAR_FIND_BIGGEST_OBJECT | CV_HAAR_DO_ROUGH_SEARCH;

    // How detailed should the search be.

    float search_scale_factor = 1.1f;

    IplImage *detectImg;

    IplImage *greyImg = 0;

    CvMemStorage* storage;

    CvRect rc;

    //double t;

    CvSeq* rects;

    CvSize size;

    int nFaces;

    //int i, ms;

    storage = cvCreateMemStorage(0);

    cvClearMemStorage( storage );

    // If the image is color, use a greyscale copy of the image.

    detectImg = (IplImage*)inputImg;

    if (inputImg->nChannels > 1) {

        size = cvSize(inputImg->width, inputImg->height);

        greyImg = cvCreateImage(size, IPL_DEPTH_8U, 1 );

        cvCvtColor( inputImg, greyImg, CV_BGR2GRAY );

        detectImg = greyImg; // Use the greyscale image.

    }

    // Detect all the faces in the greyscale image.

    //t = (double)cvGetTickCount();

    rects = cvHaarDetectObjects( detectImg, cascade, storage,

    search_scale_factor, 3, flags, minFeatureSize);

    //t = (double)cvGetTickCount() - t;

    //ms = cvRound( t / ((double)cvGetTickFrequency() * 1000.0) );

    nFaces = rects->total;

    //printf("Face Detection took %d ms and found %d objects\n", ms, nFaces);

    // Get the first detected face (the biggest).

    if (nFaces > 0)

        rc = *(CvRect*)cvGetSeqElem( rects, 0 );

    else

        rc = cvRect(-1,-1,-1,-1); // Couldn't find the face.

    if (greyImg)

    {

        cvReleaseImage( &greyImg );

    }

    cvReleaseMemStorage( &storage );

    return rc; // Return the biggest face found, or (-1,-1,-1,-1).

}