Detecting a face and saving the detected face in OpenCV - c

Question

I am trying to detect the face in the image and trying to save the detected face as an image in OpenCV.
Having some problems in the detectfaces function below.
#include "stdafx.h"
#include <stdio.h>
#include <cv.h>
#include <highgui.h>
#include <cxcore.h>
CvHaarClassifierCascade *cascade;
CvMemStorage *storage;
void detectFaces( IplImage *img );
int _tmain(int argc, _TCHAR* argv[])
{
//CvCapture *capture;
IplImage *img;//*out;
int key = 0;
char *filename = "C:/OpenCV2.1/data/haarcascades/haarcascade_frontalface_alt.xml";
cascade = ( CvHaarClassifierCascade* )cvLoad( filename, 0, 0, 0 );
storage = cvCreateMemStorage( 0 );
img = cvLoadImage("Yurico.png");
assert( cascade && storage && img );
cvNamedWindow( "video:", 1 );
//cvNamedWindow( "video1:", 1 );
//out = detectFaces( img );
detectFaces( img );
cvWaitKey( 0 );
//cvShowImage( "video", out );
cvDestroyWindow( "video:" );
//cvDestroyWindow( "video1:" );
cvReleaseImage( &img );
cvReleaseHaarClassifierCascade( &cascade );
cvReleaseMemStorage( &storage );
return 0;
}
void detectFaces( IplImage *img )
{
int i;
CvRect *r;
CvSeq *faces = cvHaarDetectObjects(
img,
cascade,
storage,
1.1,
3,
0 /*CV_HAAR_DO_CANNY_PRUNNING*/,
cvSize( 40, 40) );
for( i = 0 ; i < ( faces ? faces->total : 0 ) ; i++ ) {
CvRect *r = ( CvRect* )cvGetSeqElem( faces, i );
cvRectangle( img,
cvPoint( r->x, r->y ),
cvPoint( r->x + r->width, r->y + r->height ),
CV_RGB( 255, 0, 0 ), 1, 8, 0 );
}
//cvShowImage( "video:", img );
cvSetImageROI(img, CvRect *r);
IplImage *img2 = cvCreateImage(cvGetSize(img),
img->depth,
img->nChannels);
cvSaveImage("Lakshmen.jpg",img2);
}
Have a error saying this :
Error 1 error C2664: 'cvSetImageROI' : cannot convert parameter 2 from 'CvRect *' to 'CvRect' c:\users\hp\documents\visual studio 2010\projects\facedetect\facedetect\facedetect.cpp 67 1 facedetect
Want to save the region of interest into another image. Any corrections or improvements do tell me..

Answer 1

you need to pass a CvRect and not a CvRect*, so you do not need the pointer (*) before r.
and since it is already a cvRect you should just write:
cvSetImageROI(img, &r);

Answer 2

cvSetImageROI() takes a cvRect as the 2nd argument, and it uses it as input parameter to clip the image to that area.
In other words, you need to create a cvRect with valid info. You can do it before calling the function, or inline:
cvSetImageROI(img_corr, cvRect(x_pos, y_pos, width, height));
I also noticed that in your code, you create CvRect* r; on at least 3 diferent locations inside the same function. Bad practice! Tip: create variables in your code at the moment you are going to use them, not before that.

Answer 3

Just replace the CvRect *r as r=(CvRect*)cvGetSeqElem( faces,i) and after the for-loop write the two lines
cvSetImageROI(img, cvRect(r->x,r->y,r->width,r->height));
cvSaveImage("C1.jpg",img);