#include <highgui.h>
#include <stdio.h>
#include <cv.h>
 
CvHaarClassifierCascade *cascade;
CvMemStorage *storage;
 
int main(int argc, char *argv[]) {
    CvCapture *video = NULL;
    IplImage *frame = NULL;
    int delay = 0, key, i=0;
    char *window_name = "Video";
    char *cascadefile = "haarcascade_frontalface_alt.xml";
 
    /* check for video file passed by command line */
    if (argc>1) {
        video = cvCaptureFromFile(argv[1]);
    }
    else {
        printf("Usage: %s VIDEO_FILE\n", argv[0]);
        return 1;
    }
 
    /* check file was correctly opened */
    if (!video) {
        printf("Unable to open \"%s\"\n", argv[1]);
        return 1;
    }
 
    /* load the classifier */
    cascade = ( CvHaarClassifierCascade* )cvLoad( cascadefile, 0, 0, 0 );
    if(!cascade){
        printf("Error loading the classifier.");
	return 1;
    }
 
    /* setup the memory buffer for the face detector */
    storage = cvCreateMemStorage( 0 );
    if(!storage){
        printf("Error creating the memory storage.");
	return 1;
    }
 
    /* create a video window, auto size */
    cvNamedWindow(window_name, CV_WINDOW_AUTOSIZE);
 
    /* get a frame. Necessary for use the cvGetCaptureProperty */
    frame = cvQueryFrame(video);
 
    /* calculate the delay between each frame and display video's FPS */
    printf("%2.2f FPS\n", cvGetCaptureProperty(video, CV_CAP_PROP_FPS));
    delay = (int) (1000/cvGetCaptureProperty(video, CV_CAP_PROP_FPS));
 
    while (frame) {
	/* show loaded frame */
        cvShowImage(window_name, frame);
 
	/* wait delay and check for the quit key */
        key = cvWaitKey(delay);
        if(key=='q') break;
	/* load and check next frame*/
        frame = cvQueryFrame(video);
	if(!frame) {
		printf("error loading frame.\n");
		return 1;
	}
 
        /* detect faces */
        CvSeq *faces = cvHaarDetectObjects(
            frame, /* image to detect objects in */
            cascade, /* haar classifier cascade */
            storage, /* resultant sequence of the object candidate rectangles */
            1.1, /* increse window by 10% between the subsequent scans*/
            3, /* 3 neighbors makes up an object */
            0 /* flags CV_HAAR_DO_CANNY_PRUNNING */,
            cvSize( 40, 40 )
        );
 
        /* for each face found, draw a red box */
        for( i = 0 ; i < ( faces ? faces->total : 0 ) ; i++ ) {
             CvRect *r = ( CvRect* )cvGetSeqElem( faces, i );
             cvRectangle( frame,
                  cvPoint( r->x, r->y ),
                  cvPoint( r->x + r->width, r->y + r->height ),
                  CV_RGB( 255, 0, 0 ), 1, 8, 0 );
        }
    }
}