camera_shm/test/display.cpp

#include <opencv2/opencv.hpp>
#include <opencv2/imgcodecs.hpp>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <semaphore.h>
#include <unistd.h>
#include <iostream>
#include <string>

const int WIDTH = 640;
const int HEIGHT = 480;
const size_t SHM_SIZE = HEIGHT * WIDTH * 3; // 假设图像为640x480，RGB格式

class SharedMemoryReader {
private:
    int camera_id;
    std::string shm_name;
    std::string sem_name;
    int shm_fd;
    void* shm_ptr;
    sem_t* sem;

public:
    SharedMemoryReader(int id)
        : camera_id(id),
          shm_name("/camera_data_" + std::to_string(id)),
          sem_name("/camera_semaphore_" + std::to_string(id)),
          shm_fd(-1),
          shm_ptr(nullptr),
          sem(nullptr) {
        // 打开共享内存
        shm_fd = shm_open(shm_name.c_str(), O_RDONLY, 0666);
        if (shm_fd == -1) {
            throw std::runtime_error("Failed to open shared memory for camera " + std::to_string(camera_id));
        }

        // 将共享内存映射到进程地址空间
        shm_ptr = mmap(0, SHM_SIZE, PROT_READ, MAP_SHARED, shm_fd, 0);
        if (shm_ptr == MAP_FAILED) {
            throw std::runtime_error("Failed to map shared memory for camera " + std::to_string(camera_id));
        }

        // 打开信号量
        sem = sem_open(sem_name.c_str(), 0);
        if (sem == SEM_FAILED) {
            throw std::runtime_error("Failed to open semaphore for camera " + std::to_string(camera_id));
        }
    }

    ~SharedMemoryReader() {
        // 释放共享内存
        if (shm_ptr != nullptr) {
            munmap(shm_ptr, SHM_SIZE);
        }
        if (shm_fd != -1) {
            close(shm_fd);
        }

        // 关闭信号量
        if (sem != nullptr) {
            sem_close(sem);
        }
    }

    void read_and_display() {
        cv::Mat frame(HEIGHT, WIDTH, CV_8UC3); // 假设图像为 640x480 的 RGB 格式
        while (true) {
            // 等待信号量通知
            sem_wait(sem);

            // 从共享内存中读取数据
            std::memcpy(frame.data, shm_ptr, SHM_SIZE);
            static int count = 0;
            count++;

            // 显示图像
            // cv::imshow("Camera " + std::to_string(camera_id), frame);
            cv:imwrite("./test_"+ std::to_string(count)+".jpg", frame);
            std::cout << "Camera " << camera_id << " frame " << count << " saved.\n";

            // 按 ESC 键退出
            if (cv::waitKey(30) == 27) {
                break;
            }
        }
    }
};

int main() {
    try {
        // 假设读取相机 0 的共享内存
        SharedMemoryReader reader(0);
        reader.read_and_display();
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }

    return 0;
}