undefined values error on values that are defined

Question

I have a for loop like so

 for (int i = 0; i < circles->total; i++)
    {
         // round the floats to an int
         float* p = (float*)cvGetSeqElem(circles, i);
         cv::Point center(cvRound(p[0]), cvRound(p[1]));
         int radius = cvRound(p[2]);
         int num_red = 0;
         //uchar* ptr;
         //ptr = cvPtr2D(img, center.y, center.x, NULL);
         //printf("B: %d G: %d R: %d\n", ptr[0],ptr[1],ptr[2]);
         CvScalar s;

         s = cvGet2D(img,center.y, center.x);//colour of circle
        printf("B: %f G: %f R: %f\n",s.val[0],s.val[1],s.val[2]);

        if (s.val[2]<=255 && s.val[2]>=230 && s.val[1]<=40 && s.val[1]>=0 && s.val[0] <=40 && s.val[0]>=0)
        {
            printf("Red Ball\n");
            num_red++;
        }

which is working. but later on in my code i tried to use the s.val[] and num_red like this

int count_red = 0;
int red_pot = 0;
if(s.val[2]<=255 && s.val[2]>=230 && s.val[1]<=40 && s.val[1]>=0 && s.val[0] <=40 && s.val[0]>=0)
    count_red ++;//count the reds detected
num_red - count_red = red_pot;//originally detected - whats left = whats potted

im getting undeclared identifier error for 's'. Left of .val must have class/struct and 'num_red' : undeclared identifier. I dont understand why the program doesnt can't read these values from above further down. anyone able to help?

Answer 1

You create s inside the for loop. So as soon as the for loop terminates, s goes out of scope. You need to create a variable at a scope that includes every scope in which you intend to access it.