opencv-python- study notes four (create slider)

Create a track bar with the specified window Binding

Common functions:

createTrackbar () to create a window with sliders and binding

cv.createTrackbar(trackbarname,winname,value,count,onChange,userdata)

trackbarname: track bar name

winname: Binding window name

value: The initial position of the slider

count: the maximum slide

onChange: callback function

userdata: data, optional

getTrackbarPos () Gets data slider

cv.getTrackbarPos(trackbarname, winname)

trackbarname: slider name

winname: window name

Return value: The current position of the slider

Comprehensive Example:

import numpy as np
import cv2 as cv


def nothing(x):
    pass


# Create a black image, a window
img = np.zeros((300, 512, 3), np.uint8)
cv.namedWindow('image')
# create trackbars for color change
cv.createTrackbar('R', 'image', 0, 255, nothing)
cv.createTrackbar('G', 'image', 0, 255, nothing)
cv.createTrackbar('B', 'image', 0, 255, nothing)
while(1):
    cv.imshow('image', img)
    k = cv.waitKey(1) & 0xFF
    if k == 27:
        break
    # get current positions of four trackbars
    r = cv.getTrackbarPos('R', 'image')
    g = cv.getTrackbarPos('G', 'image')
    b = cv.getTrackbarPos('B', 'image')
    # s = cv.getTrackbarPos(switch, 'image')
    img[:] = [b, g, r]
cv.destroyAllWindows()