Face Recognition using OpenCV2 and HaarCascade an Intro Part 2

After learning theory a bit in part1 now we lear how we can detect face in an image. Later we will extend this to detecting face from web cam and avi file. The code is very simple. We will load a image of a person in IplImage structure.
We also need to load haarcascader of frontal face will which enable us to detect the face in image. Opencv 2 provides many haar cascades of face, eye , nose etc which ever you want use. If you have installed openCV v2 in "C:/OpenCV2.0" ,you find it in "C:/OpenCV2.0/data/haarcascades/" Location. Now will need to call "cvHaarDetectObjects" OpenCV Function to detect the faces.

Here is the program -

#include "cv.h"
#include "highgui.h"

#include <stdio.h>
#include <stdlib.h>

#ifdef _EiC
#define WIN32
#endif

static CvMemStorage* storage_face = 0; //Memory Storage to Sore faces

static CvHaarClassifierCascade* cascade_face = 0;

void detect_and_draw( IplImage* image );

//Haar cascade - if your openc CV is installed at location C:/OpenCV2.0/
const char* cascade_name_face ="C:/OpenCV2.0/data/haarcascades/haarcascade_frontalface_alt.xml";

/////////////////////////////////////////////////////////////////////////////////

int main()
{
IplImage *image =0;
image = cvLoadImage("viv6v.jpg",1);
if(!image)
{
         printf("Error loading image\n");
         return -1;
    }

    cascade_face = (CvHaarClassifierCascade*)cvLoad( cascade_name_face, 0, 0, 0 );

    if( !cascade_face )
    {
        printf("ERROR: Could not load classifier of face cascade\n" );
        return -1;
    }

    storage_face = cvCreateMemStorage(0);
    cvNamedWindow( "result", 1 );

    // Call function to detect and Draw rectagle around face
    detect_and_draw( image);

    // Wait for key event.
    cvWaitKey(0);

    // release resourses
    cvReleaseImage( &image );
cvReleaseHaarClassifierCascade(&cascade_face );
cvReleaseMemStorage( &storage_face);
    cvDestroyWindow("result");

    return 0;
}

//////////////////////////// Function To detect face //////////////////////////

void detect_and_draw( IplImage* img )
{

    double scale = 2;

    // create a gray image for the input image
    IplImage* gray = cvCreateImage( cvSize(img->width,img->height), 8, 1 );
    // Scale down the ie. make it small. This will increase the detection speed
    IplImage* small_img = cvCreateImage( cvSize( cvRound (img->width/scale),cvRound (img->height/scale)),8, 1 );

    int i;

    cvCvtColor( img, gray, CV_BGR2GRAY );

cvResize( gray, small_img, CV_INTER_LINEAR );

// Equalise contrast by eqalizing histogram of image
    cvEqualizeHist( small_img, small_img );

cvClearMemStorage( storage_face);

    if( cascade_face )
    {
         // Detect object defined in Haar cascade. IN our case it is face
         CvSeq* faces = cvHaarDetectObjects( small_img, cascade_face, storage_face,
                                            1.1, 2, 0/*CV_HAAR_DO_CANNY_PRUNING*/,
                                            cvSize(30, 30) );

        // Draw a rectagle around all detected face
        for( i = 0; i < (faces ? faces->total : 0); i++ )
        {
            CvRect r = *(CvRect*)cvGetSeqElem( faces, i );
   cvRectangle( img, cvPoint(r.x*scale,r.y*scale),cvPoint((r.x+r.width)*scale,(r.y+r.height)*scale),CV_RGB(255,0,0),3,8,0 );

}
    }

    cvShowImage( "result", img );
    cvReleaseImage( &gray );
    cvReleaseImage( &small_img );
}

/////////////////////////////////////////////////////////////////////////////////
</stdlib.h></stdio.h>

Output - Image with 1 Face -