opencv在视频上添加滑动条

#include 
#include 
#include 

//-----------------------------------【命名空间声明部分】---------------------------------------
//	描述：包含程序所使用的命名空间
//-----------------------------------------------------------------------------------------------
using namespace cv;
using namespace std;

//-----------------------------------【全局函数声明部分】--------------------------------------
//	描述：全局函数声明
//-----------------------------------------------------------------------------------------------
Mat img;
int threshval = 160;			//轨迹条滑块对应的值，给初值160

								//-----------------------------【on_trackbar( )函数】------------------------------------
								//	描述：轨迹条的回调函数
								//-----------------------------------------------------------------------------------------------
static void on_trackbar(int, void*)
{
	Mat bw = threshval < 128 ? (img < threshval) : (img > threshval);

	//定义点和向量
	vector > contours;
	vector hierarchy;

	//查找轮廓
	findContours(bw, contours, hierarchy, RETR_CCOMP, CHAIN_APPROX_SIMPLE);
	//初始化dst
	Mat dst = Mat::zeros(img.size(), CV_8UC3);
	//开始处理
	if (!contours.empty() && !hierarchy.empty())
	{
		//遍历所有顶层轮廓，随机生成颜色值绘制给各连接组成部分
		int idx = 0;
		for (; idx >= 0; idx = hierarchy[idx][0])
		{
			Scalar color((rand() & 255), (rand() & 255), (rand() & 255));
			//绘制填充轮廓
			drawContours(dst, contours, idx, color, FILLED, 8, hierarchy);
		}
	}
	//显示窗口
	imshow("Connected Components", dst);
	waitKey(80);
}


//-----------------------------------【main( )函数】--------------------------------------------
//	描述：控制台应用程序的入口函数，我们的程序从这里开始
//-----------------------------------------------------------------------------------------------
int main()
{
	//system("color 5F");
	////载入图片
	//img = imread("123.jpg", 0);
	//if (!img.data) { printf("Oh，no，读取img图片文件错误~！ \n"); return -1; }

	////显示原图
	//namedWindow("Image", 1);
	//imshow("Image", img);

	////创建处理窗口
	//namedWindow("Connected Components", 1);
	////创建轨迹条
	//createTrackbar("Threshold", "Connected Components", &threshval, 255, on_trackbar);
	//on_trackbar(threshval, 0);//轨迹条回调函数


	system("color 5F");
	//载入图片
	VideoCapture cap("one-by-one-person-detection.mp4");
	//img = imread("one-by-one-person-detection.mp4", 0);
	for (;;) {
		
		cap >> img;
		cvtColor(img, img,COLOR_BGR2GRAY);
		if (!img.data) { printf("Oh，no，读取img图片文件错误~！ \n"); return -1; }

		//显示原图
		namedWindow("Image", 1);
		imshow("Image", img);

		//创建处理窗口
		namedWindow("Connected Components", 1);
		//创建轨迹条
		createTrackbar("Threshold", "Connected Components", &threshval, 255, on_trackbar);
		on_trackbar(threshval, 0);//轨迹条回调函数

	}



	waitKey(0);
	return 0;
}