OpenCV学习笔记5-滑动条的使用

1.相关函数

• cv2.createTrackbar(滑动条名称，放置窗口名称，滑动条默认初始值，滑动条最大值，回调函数)
• cv2.getTrackbarPos(滑动条名称，放置窗口名称)

2.示例代码

创建一个窗口，绑定四个滑动条，其中三个分别名为R、G、B，范围为0-255，另一个是开关取值0/1，当开关取值1时，R、G、B值的变化会实时显示到图像上。

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import numpy as npimport cv2#回调函数：不做任何处理def nothing(x):    pass#创建黑底图img = np.zeros((300,512,3), np.uint8)cv2.namedWindow('image')#创建RGB三个滑动条cv2.createTrackbar('R', 'image', 0, 255, nothing)cv2.createTrackbar('G', 'image', 0, 255, nothing)cv2.createTrackbar('B', 'image', 0, 255, nothing)#创建转换按钮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:    #按下Esc键退出        break    r = cv2.getTrackbarPos('R', 'image')    g = cv2.getTrackbarPos('G', 'image')    b = cv2.getTrackbarPos('B', 'image')    s = cv2.getTrackbarPos(switch, 'image')    if s==0:        img[:]=0    else:        img[:]=[b,g,r]cv2.destroyAllWindows()

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3.进阶程序

通过滑动条，控制画笔颜色，使用鼠标绘图。

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import numpy as npimport cv2#回调函数：不做任何处理def nothing(x):    passdrawing = Falsemode = Trueix, iy = -1, -1def draw_circle(event, x, y, flags, param):    r = cv2.getTrackbarPos('R', 'image')    g = cv2.getTrackbarPos('G', 'image')    b = cv2.getTrackbarPos('B', 'image')    color = (b, g, r)    global ix, iy, drawing, mode   #注意要定义成全局变量    if event==cv2.EVENT_LBUTTONDOWN:        drawing = True        ix, iy = x, y    elif event==cv2.EVENT_MOUSEMOVE and flags==cv2.EVENT_FLAG_LBUTTON:    #鼠标移动，且左键按下时，可以画图         if drawing==True:            if mode==True:                cv2.rectangle(img, (ix, iy), (x, y), color, -1)            else:                cv2.circle(img, (x, y), 3, color, -1)    elif event==cv2.EVENT_LBUTTONUP:    #左键抬起，退出画图        drawing==Falseimg = np.zeros((512,512,3), np.uint8)cv2.namedWindow('image')cv2.createTrackbar('R', 'image', 0, 255, nothing)cv2.createTrackbar('G', 'image', 0, 255, nothing)cv2.createTrackbar('B', 'image', 0, 255, nothing)cv2.setMouseCallback('image', draw_circle)while(1):    cv2.imshow('image',img)    k = cv2.waitKey(1)&0xFF    if k==ord('m'):        mode = not mode    elif k==27:        break

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