（线性混合）创建滑动条：createTrackbar()

#include<opencv2opencv.hpp>
#include<iostream>
#include<vector>
using namespace cv;
using namespace std;

#define WINDOW_NAME "【线性混合示例】"
const int g_nMaxAlphaValue = 100;    //Alpha的最大值
int g_nAlphaValueSlider;
double g_dAlphaValue;
double g_dBetaValue;
Mat g_srcImage1;
Mat g_srcImage2;
Mat g_dstImage;

void on_Trackbar(int, void*) {
    //求出当前alpha值相对于最大值的比例
    g_dAlphaValue = (double)g_nAlphaValueSlider / g_nMaxAlphaValue;
    //则beta值为1减去alpha值
    g_dBetaValue = (1.0 - g_dAlphaValue);

    //根据alpha和beta值进行线性混合
    addWeighted(g_srcImage1,g_dAlphaValue,g_srcImage2,g_dBetaValue,0.0,g_dstImage);

    //显示效果图
    imshow(WINDOW_NAME,g_dstImage);
}
int main(int argc,char** argv) {
    g_srcImage1 = imread("C:\Users\Nelsoner\Desktop\Camera Roll\05.jpg");
    g_srcImage2 = imread("C:\Users\Nelsoner\Desktop\Camera Roll\08.jpg");

    if (!g_srcImage1.data) {
        cout << "读取第一幅图片错误！" << endl;
        return -1;
    }
    if (!g_srcImage2.data) {
        cout << "读取第二幅图片错误！" << endl;
        return -1;
    }
    //设置滑动条初值为70
    g_nAlphaValueSlider = 70;

    namedWindow(WINDOW_NAME);

    //在创建的窗体中创建一个滑动条控件
    char TrackbarName[50];
    sprintf(TrackbarName,"透明值 %d",g_nMaxAlphaValue);

    createTrackbar(TrackbarName,WINDOW_NAME, &g_nAlphaValueSlider,g_nMaxAlphaValue,on_Trackbar);

    on_Trackbar(g_nAlphaValueSlider,0);


    waitKey();
    return 0;
}

效果图：

获取当前轨迹条的位置：getTrackbarPos();