Trackbar
1.1
回调函数
定义:由系统调用,由用户实现
1.2
信号和消息循环
Ø GUI 编程中常用消息循环阻塞主线程,使其一直处于侦听事件状态
Ø 利用消息路由机制分辨出用户触发了哪类消息,用来调用用户自己实现回
调函数
import cv2 as cv import argparse alpha_slider_max=100 title_window='Linear Blend' def on_trackbar(val): alpha=val/alpha_slider_max beta=(1.0-alpha) dst=cv.addWeighted(src1,alpha,src2,beta,0.0) cv.imshow(title_window,dst) src1=cv.imread('D:/lena.jpg') src2=cv.imread('D:/box.png') if src1 is None: print('Could not open or find the image:',args.input1) exit(0) if src2 is None: print('Could not open or find the image:',args.input2) exit(0) src2=cv.resize(src2,(500,496)) cv.namedWindow(title_window) trackbar_name='Alpha x %d'%alpha_slider_max cv.createTrackbar(trackbar_name,title_window,0,alpha_slider_max,on_trackbar) # Show some stuff on_trackbar(0) # Wait untill user press some key cv.waitKey()