import cv2 as cv
import numpy as np

img = np.zeros((512, 512, 3), np.uint8)
cv.namedWindow('imag', cv.WINDOW_NORMAL)
cv.resizeWindow('imag', 510, 510)

def nothing(x):
 pass

# 参数依次为：设置轨迹(跟踪)栏名字，挂载的窗体， 默认值， 最大值，回调函数
cv.createTrackbar('R', 'imag', 0, 255, nothing) # R的值——nothing传入一个空函数体，不执行任何回调函数
cv.createTrackbar('G', 'imag', 0, 255, nothing) # G的值
cv.createTrackbar('B', 'imag', 0, 255, nothing) # B的值

switch = '1:ON\n0:OFF'
cv.createTrackbar(switch, 'imag', 0, 1, nothing) 
 # 设置一个开关——当为1时，图片背景可以改变——否则为黑色

 while True:
  cv.imshow('imag', img)
  k = cv.waitKey(1) & 0xFF
  if k == 27: # ESC退出
   break
  if cv.getTrackbarPos(switch, 'imag') == 1: # 当swtch轨迹(跟踪)栏的值为1时，允许改变背景色
   img[:] = [cv.getTrackbarPos('B', 'imag'), cv.getTrackbarPos('G', 'imag'), cv.getTrackbarPos('R', 'imag')]
   # getTrackbarPos的参数为：读取值的轨迹(跟踪)栏名，所在的窗体名
   # opencv的颜色为BGR——依次获取轨迹(跟踪)栏的值就可以了~
  else: # 否则为默认黑色
   img[:] = 0
 cv.destroyAllWindows()

import cv2 as cv
import numpy as np
def nothing(x):
 pass

if __name__ == "__main__":
 img = np.zeros((512, 512, 3), np.uint8)
 cv.namedWindow('imag', cv.WINDOW_NORMAL)
 cv.resizeWindow('imag', 510, 510)

 cv.createTrackbar('R', 'imag', 0, 255, nothing)
 cv.createTrackbar('G', 'imag', 0, 255, nothing)
 cv.createTrackbar('B', 'imag', 0, 255, nothing)
 
 switch = '1:ON\n0:OFF'
 cv.createTrackbar(switch, 'imag', 0, 1, nothing)
 while True:
  cv.imshow('imag', img)
  k = cv.waitKey(1) & 0xFF
  if k == 27:
   break
  if cv.getTrackbarPos(switch, 'imag') == 1:
   img[:] = [cv.getTrackbarPos('B', 'imag'), cv.getTrackbarPos('G', 'imag'), cv.getTrackbarPos('R', 'imag')]
  else:
   img[:] = 0
 cv.destroyAllWindows()

import cv2 as cv
import numpy as np
drawing = False
line_size = 2


def mouse_function(event, x, y, flags, param): # 鼠标回调函数——执行鼠标左键按下后移动绘图
 global drawing, line_size
 if event == cv.EVENT_LBUTTONDOWN:
  drawing = True
 elif event == cv.EVENT_MOUSEMOVE:
  if drawing is True:
   cv.circle(img, (x, y), line_size, (0, 125, 255), -1, cv.LINE_AA)
 elif event == cv.EVENT_LBUTTONUP:
  drawing = False
  cv.circle(img, (x, y), line_size, (0, 125, 255), -1, cv.LINE_AA)

# 这里不需要任何操作~所以用pass空函数体即可
def nothing(x):
 pass

__main__主体代码
if __name__ == "__main__":
 img = np.zeros((512, 512, 3), np.uint8)
 cv.namedWindow('imag', cv.WINDOW_NORMAL)
 cv.resizeWindow('imag', 510, 510)
 cv.setMouseCallback('imag', mouse_function) # 实现鼠标回调函数

 cv.createTrackbar('R', 'imag', 0, 255, nothing) # 设置R轨迹(跟踪)栏
 cv.createTrackbar('G', 'imag', 0, 255, nothing)
 cv.createTrackbar('B', 'imag', 0, 255, nothing)
 
 switch = '1:ON\n0:OFF'
 cv.createTrackbar(switch, 'imag', 0, 1, nothing) # 设置开关控制轨迹(跟踪)栏

 while True:
  cv.imshow('imag', img)
  k = cv.waitKey(1) & 0xFF
  if k == 27:
   break
  if cv.getTrackbarPos(switch, 'imag') == 1: # 为1是，刷新画面
   img[:] = [cv.getTrackbarPos('B', 'imag'), cv.getTrackbarPos('G', 'imag'), cv.getTrackbarPos('R', 'imag')]
   cv.setTrackbarPos(switch, 'imag', 0) # 通过set轨迹(跟踪)栏位置，实现为1刷新后，及时回到0位置
 cv.destroyAllWindows()