i think you can use this code
convert image to grayscale image
gray_image = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
convert the grayscale image to binary image
ret,thresh = cv2.threshold(gray_image,127,255,0)
calculate moments of binary image
M = cv2.moments(thresh)
calculate x,y coordinate of center
cX = int(M["m10"] / M["m00"])
cY = int(M["m01"] / M["m00"])
put text and highlight the center
cv2.circle(img, (cX, cY), 5, (255, 255, 255), -1)
cv2.putText(img, "centroid", (cX - 25, cY - 25),cv2.FONT_HERSHEY_SIMPLEX, 0.5, (255, 255, 255), 2)
display the image
cv2.imshow("Image", img)
cv2.waitKey(0)
