05 trackbar用法

# createTrackbar(trackbarname, winname, value, count, onChange)创建TrackBar控件，value为trackbar的默认值，count为bar的最大值，最小值为0

# getTrackbarPos(trackbarname, winname)获取TrackBar当前值

# createTrackbar(trackbarname, winname, value, count, onChange)创建TrackBar控件，value为trackbar的默认值
# count为bar的最大值，最小值为0

# getTrackbarPos(trackbarname, winname)获取TrackBar当前值

# trackbar demo
import cv2
import numpy as np

# 创建窗口
cv2.namedWindow('trackbar', cv2.WINDOW_NORMAL)
cv2.resizeWindow('trackbar', 640, 480)


# 定义回调函数
def callback(value):
    # print(value)
    pass


# 创建三个trackbar
cv2.createTrackbar('R', 'trackbar', 0, 255, callback)
cv2.createTrackbar('G', 'trackbar', 0, 255, callback)
cv2.createTrackbar('B', 'trackbar', 0, 255, callback)

# 创建背景图片
img = np.zeros((480, 640, 3), np.uint8)
while True:
    # 获取当前trackbar的值
    r = cv2.getTrackbarPos('R', 'trackbar')
    g = cv2.getTrackbarPos('G', 'trackbar')
    b = cv2.getTrackbarPos('B', 'trackbar')

    # 用获取到的三个值修改背景图片颜色
    # 将第三个维度的值取出来
    img[:] = [b, g, r]
    cv2.imshow('trackbar', img)
    key = cv2.waitKey(1)
    if key == ord('q'):
        break

cv2.destroyAllWindows()