案例實戰

1、簡易調色板

def ColorPalette():
    # 簡易調色板
    def callback(value):
        print(value)
    # trackbar控件
    cv2.namedWindow("trackbar",cv2.WINDOW_NORMAL)
    cv2.resizeWindow("trackbar",640,480)
    cv2.createTrackbar("R","trackbar",0,255,callback)
    cv2.createTrackbar("G","trackbar",0,255,callback)
    cv2.createTrackbar("B","trackbar",0,255,callback)


    bg = np.zeros((480,640,3),np.uint8)


    while True:
        r = cv2.getTrackbarPos("R","trackbar")
        g = cv2.getTrackbarPos("G", "trackbar")
        b = cv2.getTrackbarPos("B", "trackbar")
        bg[:] = [b,g,r]
        cv2.imshow("trackbar",bg)
        key = cv2.waitKey(20)
        if key == 27:
            break
    cv2.destroyAllWindows()


# ColorPalette()

2、創建畫布，按下指定鍵畫指定圖案

def CaptureShape(img):
    # 創建畫布，按下指定鍵畫指定圖案
    cur_shape = 0
    # 初始坐標
    start_pos = (0,0)


    def mouse_callback(event,x,y,flags,userdata):
        nonlocal start_pos,cur_shape
        # 鼠標按下
        if event == cv2.EVENT_LBUTTONDOWN:
            start_pos = (x,y)
        # 鼠標松開
        elif event == cv2.EVENT_LBUTTONUP:
            if cur_shape == 0:
                cv2.line(img,start_pos,(x,y),(0,255,255),2)
            elif cur_shape == 1:
                cv2.rectangle(img,start_pos,(x,y),(255,0,255),2)
            elif cur_shape==2:
                a = (x-start_pos[0])
                b = (y-start_pos[1])
                r = int((a**2+b**2)**0.5)
                cv2.circle(img,start_pos,r,(255,255,0),2)
            else:
                print("not support")


    cv2.namedWindow('draw',cv2.WINDOW_NORMAL)
    cv2.setMouseCallback('draw',mouse_callback)


    while True:
        # 按下l鍵畫直線，按下r鍵畫矩形，按下c鍵畫圓
        cv2.imshow('draw',img)
        key = cv2.waitKey(1)
        if key == 27:
            break
        elif key == ord("l"):
            cur_shape = 0
        elif key == ord("r"):
            cur_shape =1
        elif key == ord("c"):
            cur_shape =2


    cv2.destroyAllWindows()
# img = np.zeros([500,500,3],np.uint8)
# CaptureShape(img)

3、人臉檢測

def FaceDetect():
    # 人臉檢測
    face_detector = cv2.CascadeClassifier("./haarcascade_frontalface_alt.xml")
    while True:
        cap = cv2.VideoCapture(0)
        ret,frame = cap.read()
        gray = cv2.cvtColor(frame,code=cv2.COLOR_BGR2GRAY)
        face = face_detector.detectMultiScale(gray)
        for x,y,w,h in face:
            cv2.circle(frame,(x+w//2,y+h//2),w//2,(0,255,255),2)
        cv2.imshow("img",frame)
        key = cv2.waitKey(20)
        if key == 27:
            break
    cap.release()
    cv2.destroyAllWindows()