完整可运行代码如下

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/objdetect.hpp>
#include "opencv2/imgproc/imgproc.hpp"
#include <stdio.h>
using namespace std;
using namespace cv;

int main()
{
    Mat img;
    vector<Rect> found;
    img = imread("/home/cubot/models/timg.jpeg");
    if(!img.data)
    {
        printf("没有图片\n");
        return -1;
    }
    HOGDescriptor defaultHog;
    defaultHog.setSVMDetector(HOGDescriptor::getDefaultPeopleDetector());
    //进行检测
    defaultHog.detectMultiScale(img, found);
    //画长方形，框出行人
    for(int i = 0; i < found.size(); i++)
    {
        Rect r = found[i];
        rectangle(img, r.tl(), r.br(), Scalar(0, 0, 255), 3);
    }
    namedWindow("检测行人", CV_WINDOW_AUTOSIZE);
    imshow("检测行人", img);
    waitKey(0);

    return 0;
}

效果如下