opencv学习笔记03-鼠标回调与trackbar

opencv 简易笔记 3--鼠标回调与 trackbar

1.设置鼠标回调函数

import cv2
import numpy

def mouse_callback(event, x, y, flags, userdata):
    if event == 1:
        print(event, x, y, flags, userdata)

# 窗口命名
cv2.namedWindow("mouse", cv2.WINDOW_NORMAL)
# 设置鼠标回调函数
a = cv2.setMouseCallback("mouse", mouse_callback, "userdata")
# 显示窗口
img = numpy.zeros((500, 500, 3), numpy.uint8)
while True:
    cv2.imshow("mouse", img)
    key = cv2.waitKey(0)
    # 销毁
    if key & 0xFF == ord("q"):
        cv2.destroyAllWindows()
        break

简单说明一下代码逻辑，首先需要定义一个鼠标回调函数，即 mouse_callback(event, x, y, flags, userdata),该函数原型应为：

#void on_Mouse(int event, int x, int y, int flags, void* param);
def mouse_callback(event, x, y, flags, userdata):
    print(event, x, y, flags, userdata)

其中，像event，flags均有定义：

1.1 setMouseCallback(winname,callback,para) -> None

(1) winname: 即窗口名字
(2) callback: 需要设置的回调函数
(3) para: 参数，暂定,这个 param 是 onMouse 和 setMouseCallback 之间的参数通信接口。

2.trackBar 介绍

import cv2
import numpy


def callback(any):
    pass


# 窗口命名
cv2.namedWindow("trackbar", cv2.WINDOW_NORMAL)
cv2.createTrackbar("R", "trackbar", 20, 255, callback)
cv2.createTrackbar("G", "trackbar", 20, 255, callback)
cv2.createTrackbar("B", "trackbar", 20, 255, callback)
# 显示窗口
img = numpy.zeros((500, 500, 3), numpy.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")
    print(type(r))
    # 改变背景图片颜色
    img[:] = [b, g, r]
    cv2.imshow("trackbar", img)
    key = cv2.waitKey(10)
    # 销毁
    if key & 0xFF == ord("q"):
        cv2.destroyAllWindows()
        break

2.1 createTrackbar(trackbarName,windowName,value,count,onchange) ->

(1) trackbarName: trackbar 名字
(2) windowName: 窗口名字
(3) value: trackbar 当前值
(4) count: trackbar 最大值
(5) onchange: 一个回调函数，在值改变时触发

2.2 getTrackbarPos() -> (int)pos

(1) trackbarName: trackbar 名字
(2) windowName: 窗口名字