i have an binary word image, a word image B is divided into 11 × 11 segments of equal size, i want to find foreground pixels and center of mass in each and every segment

 a word image B is divided into 11 × 11 segments of equal size. For each segment sij (i = 1, . . . , C; j = 1, . . . , R) a node is inserted into the resulting graph and labelled by the (x, y)-coordinates of the centre of mass (xm, ym). Formally, we compute a node is inserted into the resulting graph and labelled by the (x, y)-coordinates of the centre of mass (xm, ym). Formally, we compute 
formula to calculate centre of see 'COM.jpg' image,

where n denotes the number of foreground pixel in segment sij, while xw and yw denote the x- and y-coordinates of the foreground pixels in sij. If a segment does not contain any foreground pixel, no centre of mass can be determined and thus no node is created for this segment.