code: def mark_point(img, x, y):
      
      overlay = img.copy()
      output = img.copy()
  
      alpha = 0.5
      radius = max(5, min(img.shape[:2])//15)
      center = int(x), int(y)
      color = (0, 0, 255)
  
      cv2.circle(overlay, center, radius, color, -1)
      cv2.addWeighted(overlay, alpha, output, 1-alpha, 0, output)
      return output
docs: Mark a point
  
      Args:
          - img(numpy): the source image
          - x, y(int): position