import cv2 as cv
import numpy as np


img = cv.imread('duckie.jpg')
cv.imshow('duckie.jpg', img)
cv.waitKey(0)

while():
    _, frame = img.read()  # Take each frame
    hsv = cv.cvtColor(img, cv.COLOR_BGR2HSV)
    lower_yellow = np.array([30, 255, 255])  # define range of yellow color in HSV
    upper_yellow = np.array([[255, 255, 255]])
    # Threshold the HSV image to get only yellow
    mask = cv.inRange(hsv, lower_yellow, upper_yellow)
    # Bitwise-AND mask and original image
    res = cv.bitwise_and(frame, frame, mask=mask)
    cv.imshow('frame', frame)
    cv.imshow('mask', mask)
    cv.imshow('res', res)
    k = cv.waitKey(5) & 0xFF
    if k == 27:
        break
cv.destroyAllWindows()

# for contours
cv.drawContours(img, contours, 3, (0,255,0), 3)
im = cv.imread('duckie.jpg')
img = cv.cvtColor(im, cv.COLOR_BGR2HSV)
ret, thresh = cv.threshold(img, 127, 255, 0)
contours, hierarchy = cv.findContours(thresh, cv.RETR_TREE, cv.CHAIN_APPROX_SIMPLE)