提供一个QT在linux系统使用V4l2读取摄像头图像流数据的例程

以下是一个使用QT在Linux系统中使用V4L2读取摄像头图像流数据的例程：

#include <QCoreApplication>
#include <QDebug>
#include <QImage>
#include <QTimer>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
#include <errno.h>
#include <unistd.h>

#define CAMERA_DEVICE "/dev/video0" // 摄像头设备路径
#define IMAGE_WIDTH 640 // 图像宽度
#define IMAGE_HEIGHT 480 // 图像高度
#define BUFFER_COUNT 4 // 缓存帧数

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    int camera_fd = open(CAMERA_DEVICE, O_RDWR); // 打开摄像头设备
    if (camera_fd == -1) {
        qCritical() << "Open camera device failed:" << strerror(errno);
        return -1;
    }

    // 设置摄像头参数
    struct v4l2_capability cap;
    struct v4l2_format fmt;
    struct v4l2_requestbuffers reqbuf;
    struct v4l2_buffer buf;

    ioctl(camera_fd, VIDIOC_QUERYCAP, &cap);
    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
        qCritical() << "Device is not a video capture device";
        return -1;
    }

    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width = IMAGE_WIDTH;
    fmt.fmt.pix.height = IMAGE_HEIGHT;
    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
    fmt.fmt.pix.field = V4L2_FIELD_ANY;
    ioctl(camera_fd, VIDIOC_S_FMT, &fmt);

    reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    reqbuf.memory = V4L2_MEMORY_MMAP;
    reqbuf.count = BUFFER_COUNT;
    ioctl(camera_fd, VIDIOC_REQBUFS, &reqbuf);

    struct buffer {
        void *start;
        size_t length;
    } buffers[BUFFER_COUNT];

    for (int i = 0; i < BUFFER_COUNT; ++i) {
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = i;
        ioctl(camera_fd, VIDIOC_QUERYBUF, &buf);

        buffers[i].length = buf.length;
        buffers[i].start = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, camera_fd, buf.m.offset);

        ioctl(camera_fd, VIDIOC_QBUF, &buf);
    }

    enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    ioctl(camera_fd, VIDIOC_STREAMON, &type);

    // 定时器读取图像
    QTimer timer;
    QObject::connect(&timer, &QTimer::timeout, [&](){
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        ioctl(camera_fd, VIDIOC_DQBUF, &buf);

        QImage image((uchar*)buffers[buf.index].start, IMAGE_WIDTH, IMAGE_HEIGHT, QImage::Format_RGB888);
        image = image.rgbSwapped(); // 颜色转换
        image.save("image.jpg"); // 保存图像

        ioctl(camera_fd, VIDIOC_QBUF, &buf);
    });
    timer.start(1000 / 25); // 25帧每秒

    return a.exec();
}

注意：上述代码仅供参考，具体实现可能需要根据不同的硬件和系统做出一些调整。