import numpy as np
import cv2 as cv
from matplotlib import pyplot as plt
img = cv.imread('coin.png')
gray = cv.cvtColor(img,cv.COLOR_BGR2GRAY)
ret, thresh = cv.threshold(gray,0,255,cv.THRESH_BINARY_INV+cv.THRESH_OTSU)



kernel = np.ones((3,3),np.uint8)
opening = cv.morphologyEx(thresh,cv.MORPH_OPEN,kernel, iterations = 2)

sure_bg = cv.dilate(opening,kernel,iterations=3)

dist_transform = cv.distanceTransform(opening,cv.DIST_L2,5)
ret, sure_fg = cv.threshold(dist_transform,0.7*dist_transform.max(),255,0)

sure_fg = np.uint8(sure_fg)
unknown = cv.subtract(sure_bg,sure_fg)


ret, markers = cv.connectedComponents(sure_fg)

markers = markers+1

markers[unknown==255] = 0
markers = cv.watershed(img,markers)
img[markers == -1] = [255,0,0]
cv.imshow('img',img)
cv.waitKey(0)