import cv2
counter,cord = 0,[]
def click_event(event, x, y, flags, params):
global counter
if event == cv2.EVENT_LBUTTONDOWN:
counter=counter+1
if counter<=2:
cv2.line(img, (x, 0), (x, img.shape[0]), (255, 0, 0), 5)
cv2.line(img, (0, y), (img.shape[1],y), (255, 0, 0), 5)
cord.append([x,y])
cv2.imshow('image', img)
if counter == 2:
print(cord)
im = img[cord[0][1]:cord[1][1],cord[0][0]:cord[1][0]]
cv2.imshow('image', im)
if __name__ == "__main__":
img = cv2.imread('img.png', 1)
cv2.imshow('image', img)
cv2.setMouseCallback('image', click_event)
cv2.waitKey(0)
cv2.destroyAllWindows()