RGB Trackbar

我們將創建一個簡單的應用程序，它顯示了你指定的顏色。你有一個窗口，其中顯示的顏色和三個trackbars指定每個的B，G，R的色彩。你滑動的TrackBar和相應的窗口顏色變化

import cv2
import numpy as np

def nothing(x):
    pass

# Create a black image, a window
img = np.zeros((300,512,3), np.uint8)
cv2.namedWindow('image')

# create trackbars for color change
cv2.createTrackbar('R','image',0,255,nothing)
cv2.createTrackbar('G','image',0,255,nothing)
cv2.createTrackbar('B','image',0,255,nothing)

# create switch for ON/OFF functionality
switch = '0 : OFF \n1 : ON'
cv2.createTrackbar(switch, 'image',0,1,nothing)

while(1):
    cv2.imshow('image',img)
    k = cv2.waitKey(1) & 0xFF
    if k == 27:
        break

    # get current positions of four trackbars
    r = cv2.getTrackbarPos('R','image')
    g = cv2.getTrackbarPos('G','image')
    b = cv2.getTrackbarPos('B','image')
    print " R=",r,
    print " G=",g,
    print " B=",b
    s = cv2.getTrackbarPos(switch,'image')

    if s == 0:
        img[:] = 0
    else:
        img[:] = [b,g,r]

cv2.destroyAllWindows()

http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_gui/py_trackbar/py_trackbar.html#trackbar