滑动轨迹栏作调色板

cv.createTrackbar(‘R’, ‘image’, 0, 255, nothing)
参数：哪个滑动轨迹栏，哪个窗口，最小值，最大值，回调函数

cv.getTrackbarPos(‘R’, ‘image’)
参数：轨迹栏名，窗口名

import numpy as np
import cv2 as cv

def nothing(x):
    pass
img = np.zeros((600, 512, 3), np.uint8)
cv.namedWindow('image', 0)

cv.createTrackbar('R', 'image', 0, 255, nothing)
cv.createTrackbar('G', 'image', 0, 255, nothing)
cv.createTrackbar('B', 'image', 0, 255, nothing)

switch = 'OFF : ON'
cv.createTrackbar(switch, 'image', 0, 1, nothing)

while(1):
    cv.imshow('image', img)
    k = cv.waitKey(1) & 0xFF
    if k == 27:
        break

    r = cv.getTrackbarPos('R', 'image')
    g = cv.getTrackbarPos('G', 'image')
    b = cv.getTrackbarPos('B', 'image')

    s = cv.getTrackbarPos(switch, 'image')
    if s == 0:
        img[:] = 0
    else:
        img[:] = [b, g, r]   # *****************

cv.destroyAllWindows()