Finding Points in Contours

Question

So here is the code that i used to detect the contours:

IplImage* DetectAndDrawQuads(IplImage* img)

{
CvSeq* contours;
CvSeq* result;
CvMemStorage *storage = cvCreateMemStorage(0);

IplImage* ret = cvCreateImage(cvGetSize(img), 8, 3);
IplImage* temp = cvCreateImage(cvGetSize(img), 8, 1);

cvCvtColor(img, temp, CV_BGR2GRAY);

cvFindContours(temp, storage, &contours, sizeof(CvContour), CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE, cvPoint(0,0));

while(contours)
{
    result = cvApproxPoly(contours, sizeof(CvContour), storage, CV_POLY_APPROX_DP, cvContourPerimeter(contours)*0.10, 0); //*0.2


    if((result->total) == 4)  
    {
        CvPoint *pt[4];
        for(int i=0;i<4;i++)
            pt[i] = (CvPoint*)cvGetSeqElem(result, i);

            cvLine(ret, *pt[0], *pt[1], cvScalar(255));
            cvLine(ret, *pt[1], *pt[2], cvScalar(255));
            cvLine(ret, *pt[2], *pt[3], cvScalar(255));
            cvLine(ret, *pt[3], *pt[0], cvScalar(255));


    }

    contours = contours->h_next;

}

cvReleaseImage(&temp);
cvReleaseMemStorage(&storage);

return ret;
}


int main()

{

    IplImage* img = cvLoadImage("D:\\Database\\eye2.jpg");
IplImage* contourDrawn = 0;
cvNamedWindow("original");
cvShowImage("original", img);

contourDrawn = DetectAndDrawQuads(img);
cvNamedWindow("contours");
cvShowImage("contours", contourDrawn);

cvWaitKey(0);
return 0;
}

And this is the Pic that I used to test the program: Input

I am trying to get the contours as a preliminary step in finding the facial expression of an inputted face. And this is the Result when i tried to run the program (Original [left] and Output [right]): Result

As you can see there seems to be some noise left in the binary image (Which I actually preprocessed before it is being inputted in my find contours program (the codes above)).

My Question is:

1. How to find the points in the contours (e.g, top, bottom, center, leftmost, and rightmost --> essential points to make geometrical calculations to determine facial expression).

Thank you very much if you will help me. So far, this is the best output i could generate regarding finding contours. Also if you can help me extract the contours more accurately then that will be very much appreciated. Thank you. :)

Answer 1

cvPoint rightMost = (0, 0); 
cvPoint leftMost = (gray->width, 0);
cvPoint bottom =  (0, gray->height);
cvPoint top = (0, 0);;   
for( CvSeq* current = contours; current != NULL; current = current->h_next )
{
    for( int i = 0; i < current->total; i++ )
    {
         CvPoint* pt = (CvPoint*)cvGetSeqElem( current, i );
         int pixVal = (int)(gray->imageData + pt->x * gray->widthStep)[pt->y];
        //find the point, which coordinate X is the biggest
         if( pt->x > rightMost ) 
         {
            rightMost->x = pt->x;  
            rightMost->y = pt->y;
         }  
        //find the point, which coordinate X is the smallest
         if( pt->x < leftMost ) 
         {
            leftMost->x = pt->x;  
            leftMost->y = pt->y;
         }  
        //find the point, which coordinate Y is the biggest
         if( pt->y > top )
         {
            top->x = pt->x;  
            top->y = pt->y;
         }    
        //find the point, which coordinate Y is the smallest
         if( pt->x < bottom ) 
         {
            bottom->x = pt->x;  
            bottom->y = pt->y;
         }  

    }
}
cvPoint ptCenter(cvRound(( rightMost + leftMost ) / 2), ( top + bottom ) / 2 );

I haven't tried this code, but I think it will be helpfull!