ball collision detection

Question

im trying to detect what colour ball a white ball initially makes contact with.

the coordinates and colors of all balls are known and the video feed of the balls will be top-view so there is only coordinates in x-y

my code for the detected balls is as follows

*//draw all detected circles
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]);
     //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]);
     // draw the circle center
     cvCircle(img, center, 3, CV_RGB(0,255,0), -1, 8, 0 );
     // draw the circle outline
     cvCircle(img, center, radius+1, CV_RGB(0,0,255), 2, 8, 0 );
     //display coordinates
     printf("x: %d y: %d r: %d\n",center.x,center.y, radius);
}* 

Answer 1

Since you know the coordinates for the centers of the balls you can just calculate the euclidean distance from the white ball center each ball center. once the distance between two ball centers is the sum of their radiuses then you have your collision. Hope that helps.