在opencv4下，对摄像头进行调用显示画面，在按下p键后对当前画面进行压缩保存到路径/root/20204367yyh并从photo1开始命名，并在视频画面左上角显示“当前已保存的图片数量”，最后在按下q键后退出画面。同时给出相应的Makefile文件，注意opencv的路径为/root/opencv-4.5.1

以下是实现代码和Makefile文件：

#include <iostream>
#include <opencv2/opencv.hpp>

using namespace std;
using namespace cv;

int main() {
    VideoCapture cap(0);
    if (!cap.isOpened()) {
        cerr << "Error opening camera." << endl;
        return -1;
    }

    int photoNum = 0;
    Mat frame;
    namedWindow("Camera", WINDOW_NORMAL);

    while (true) {
        cap >> frame;
        imshow("Camera", frame);

        int key = waitKey(30);
        if (key == 'p') {
            string path = "/root/20204367yyh/photo" + to_string(++photoNum) + ".jpg";
            imwrite(path, frame);
            cout << "Save photo: " << path << endl;
        } else if (key == 'q') {
            break;
        }

        putText(frame, "Photos: " + to_string(photoNum), Point(10, 30), FONT_HERSHEY_SIMPLEX, 1, Scalar(0, 0, 255), 2);
    }

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

Makefile文件：

CC = g++
CFLAGS = -Wall -std=c++11
LDFLAGS = $(shell pkg-config --libs opencv4)

all: camera

camera: camera.cpp
	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)

clean:
	rm camera