drawMarker(...)
 drawMarker(img, position, color[, markerType[, markerSize[, thickness[, line_type]]]]) -> img
 .@brief Draws a marker on a predefined position in an image.
 .
 .The function cv::drawMarker draws a marker on a given position in the image. For the moment several
 .marker types are supported, see #MarkerTypes for more information.
 .
 .@param img Image.
 .@param position The point where the crosshair is positioned.
 .@param color Line color.
 .@param markerType The specific type of marker you want to use, see #MarkerTypes
 .@param thickness Line thickness.
 .@param line_type Type of the line, See #LineTypes
 .@param markerSize The length of the marker axis [default = 20 pixels]

# -*- coding: utf-8 -*-
import cv2
import numpy as np
if __name__ == '__main__':
 image = np.zeros((256, 256, 3), np.uint8)
 color = (0, 255, 0)
 cv2.drawMarker(image, (50, 50), color, markerType=0)
 cv2.drawMarker(image, (100, 50), color, markerType=1)
 cv2.drawMarker(image, (150, 50), color, markerType=2)
 cv2.drawMarker(image, (200, 50), color, markerType=3)
 cv2.drawMarker(image, (50, 100), color, markerType=4)
 cv2.drawMarker(image, (100, 100), color, markerType=5)
 cv2.drawMarker(image, (150, 100), color, markerType=6)
 cv2.namedWindow('marker_type', 1)
 cv2.imshow('marker_type', image)
 cv2.waitKey(0)
 cv2.destroyAllWindows()

# -*- coding: utf-8 -*-
import cv2
import numpy as np
WIN_NAME = 'pick_points'

def onmouse_pick_points(event, x, y, flags, param):
 if event == cv2.EVENT_LBUTTONDOWN:
  print('x = %d, y = %d' % (x, y))
  cv2.drawMarker(param, (x, y), (0, 255, 0))

if __name__ == '__main__':
 image = np.zeros((256, 256, 3), np.uint8)
 cv2.namedWindow(WIN_NAME, 0)
 cv2.setMouseCallback(WIN_NAME, onmouse_pick_points, image)
 while True:
  cv2.imshow(WIN_NAME, image)
  key = cv2.waitKey(30)
  if key == 27:  # ESC
break
 cv2.destroyAllWindows()

x = 60, y = 55
x = 206, y = 113
x = 114, y = 192

# -*- coding: utf-8 -*-
import cv2
import numpy as np
WIN_NAME = 'pick_points'

class DrawPoints(object):
 def __init__(self, image, color,
  marker_type=cv2.MARKER_CROSS,
  marker_size=20,
  thickness=1):
  """
  Initialization of class DrawPoints
  Parameters
  ----------
  image: ndarray
source image. shape is [height, width, channels]
  color: tuple
a tuple containing uint8 integers, designating B, G, R values,
separately
  marker_type: int
marker type, between [0, 6]
  marker_size: int
marker size, >=1
  thickness: int
line thickness, >=1
  """
  self.original_image = image
  self.image_for_show = image.copy()
  self.color = color
  self.marker_type = marker_type
  self.marker_size = marker_size
  self.thickness = thickness
  self.pts = []
 def append(self, x, y):
  """
  add a point to points list
  Parameters
  ----------
  x, y: int, int
coordinate of a point
  """
  self.pts.append((x, y))
 def pop(self):
  """
  pop a point from points list
  """
  pt = ()
  if self.pts:
pt = self.pts.pop()
  return pt
 def reset_image(self):
  """
  reset image_for_show using original image
  """
  self.image_for_show = self.original_image.copy()
 def draw(self):
  """
  draw points on image_for_show
  """
  for pt in self.pts:
cv2.drawMarker(self.image_for_show, pt, color=self.color,markerType=self.marker_type,markerSize=self.marker_size,thickness=self.thickness)

def onmouse_pick_points(event, x, y, flags, draw_pts):
 if event == cv2.EVENT_LBUTTONDOWN:
  print('add: x = %d, y = %d' % (x, y))
  draw_pts.append(x, y)
  draw_pts.draw()
 elif event == cv2.EVENT_RBUTTONDOWN:
  pt = draw_pts.pop()
  if pt:
print('delete: x = %d, y = %d' % (pt[0], pt[1]))
draw_pts.reset_image()
draw_pts.draw()

if __name__ == '__main__':
 image = np.zeros((256, 256, 3), np.uint8)
 draw_pts = DrawPoints(image, (0, 255, 0))
 cv2.namedWindow(WIN_NAME, 0)
 cv2.setMouseCallback(WIN_NAME, onmouse_pick_points, draw_pts)
 while True:
  cv2.imshow(WIN_NAME, draw_pts.image_for_show)
  key = cv2.waitKey(30)
  if key == 27:  # ESC
break
 cv2.destroyAllWindows()