opencv 代码没有检测到人脸数量也没有在人脸周围放一个圆圈

Question

我的代码：

#include "opencv2/opencv.hpp"
#include <iostream>
#include "opencv2/objdetect.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"


using namespace std;
using namespace cv;



int main()
{
    VideoCapture cap(0);


    CascadeClassifier cascade, netCascade;

    double scale = 1;

    netCascade.load("/opt/opencv/data/haarcascades/haarcascade_frontalcatface.xml");
    cascade.load("/opt/opencv/data/haarcascades/haarcascade_eye_tree_eyeglasses.xml");


    //cap.open();
    if(!cap.isOpened())
    {
        cout<<"error opening video file"<<endl;
        return -1;
    }
   
    while(1)
    {
        Mat img;
        cap>>img;

        if(img.empty())
        {
            break;
        }


        //Mat img1 = img.clone();

        vector<Rect> faces, faces2;
        Mat grey, smallImg;

        cvtColor(img, grey, COLOR_BGR2GRAY);
        double fx = 1 / scale;

        resize(grey, smallImg, Size(), fx, fx, INTER_LINEAR);
        equalizeHist(smallImg, smallImg);

        cascade.detectMultiScale(smallImg, faces, 1.1, 2, 0|CASCADE_SCALE_IMAGE, Size(30,30));

        
        cout<<"number of faces = "<<faces.size()<<endl;
        for(size_t i = 0; i < faces.size(); i++)
        {
            Rect r = faces[i];
            Mat smallImgROI;
            vector<Rect> nestedObjects;
            Point center;
            Scalar color = Scalar(255, 0, 0); // Color for Drawing tool
            int radius;
            double aspect_ratio = (double)r.width/r.height;


            if( 0.75 < aspect_ratio && aspect_ratio < 1.3 )
            {
                center.x = cvRound((r.x + r.width*0.5)*scale);
                center.y = cvRound((r.y + r.height*0.5)*scale);
                radius = cvRound((r.width + r.height)*0.25*scale);
                circle( img, center, radius, color, 3, 8, 0 );
            }
            else
                rectangle( img, cv::Point(cvRound(r.x*scale), cvRound(r.y*scale)),
                        cv::Point(cvRound((r.x + r.width-1)*scale),
                        cvRound((r.y + r.height-1)*scale)), color, 3, 8, 0);
            if( netCascade.empty() )
                continue;
            smallImgROI = smallImg( r );


        }




        imshow("video",img);

        char c = (char) waitKey(25);
        if(c == 27 || c == 'q' || c == 'Q')
        {
            break;
        }
    }

    cap.release();
    destroyAllWindows();
    return 0;
}

首先打开笔记本电脑的摄像头。 然后拍摄视频。 然后分配垫帧。然后转换为灰度图像，调整它的大小。 分配一个面向量，与 xml 文件匹配。 使用 face.size() 查找面数。 使用 cout 在命令行上打印面数（faces.size()）。在面周围绘制圆圈。 但是当我坐在它前面时，面数打印为 0。 我认为它应该打印 1。此外，它不会在脸部周围画圈。 我在哪里做错了？ 当我的脸靠近屏幕时，有时会在我的两只眼睛周围显示 2 个圆圈，但并非总是如此。 有时， faces.size() 返回 3。这怎么可能有值 3。为什么它不总是画圆？

Answer 1

要检测人脸，必须在人脸级联分类器上调用detectMultiScale 。

#include "opencv2/opencv.hpp"
#include <iostream>
#include "opencv2/objdetect.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"


using namespace std;
using namespace cv;



int main()
{
    VideoCapture cap(0);


    CascadeClassifier face_cc;

    double scale = 1;
    face_cc.load("/opt/opencv/data/haarcascades/haarcascade_frontalcatface.xml");


    //cap.open();
    if(!cap.isOpened())
    {
        cout<<"error opening video file"<<endl;
        return -1;
    }

    while(1)
    {
        Mat img;
        cap>>img;

        if(img.empty())
        {
            break;
        }


        //Mat img1 = img.clone();

        vector<Rect> faces, faces2;
        Mat grey, smallImg;

        cvtColor(img, grey, COLOR_BGR2GRAY);
        double fx = 1 / scale;

        resize(grey, smallImg, Size(), fx, fx, INTER_LINEAR);
        equalizeHist(smallImg, smallImg);

        //cascade.detectMultiScale(smallImg, faces, 1.1, 2, 0|CASCADE_SCALE_IMAGE, Size(30,30));

        //detect faces
        face_cc.detectMultiScale( smallImg, faces );


        cout<<"number of faces = "<<faces.size()<<endl;
        for(size_t i = 0; i < faces.size(); i++)
        {
            Rect r = faces[i];
            Mat smallImgROI;
            vector<Rect> nestedObjects;
            Point center;
            Scalar color = Scalar(255, 0, 0); // Color for Drawing tool
            int radius;
            double aspect_ratio = (double)r.width/r.height;


            if( 0.75 < aspect_ratio && aspect_ratio < 1.3 )
            {
                center.x = cvRound((r.x + r.width*0.5)*scale);
                center.y = cvRound((r.y + r.height*0.5)*scale);
                radius = cvRound((r.width + r.height)*0.25*scale);
                circle( img, center, radius, color, 3, 8, 0 );
            }
            else
            {
                rectangle( img, cv::Point(cvRound(r.x*scale), cvRound(r.y*scale)),
                        cv::Point(cvRound((r.x + r.width-1)*scale),
                        cvRound((r.y + r.height-1)*scale)), color, 3, 8, 0);
            }
            smallImgROI = smallImg( r );
        }

        imshow("video",img);

        char c = (char) waitKey(25);
        if(c == 27 || c == 'q' || c == 'Q')
        {
            break;
        }
    }

    cap.release();
    destroyAllWindows();
    return 0;
}