C++ 实现v4l2调用摄像头拍照

好的，以下是一个基本的 C++ 代码示例，可用于使用 V4L2 调用摄像头拍照：

#include <iostream>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>

using namespace std;

int main(int argc, char* argv[]) {
  const char* device = "/dev/video0";  // 摄像头设备名称
  int fd = open(device, O_RDWR);  // 打开设备
  if (fd == -1) {
    cerr << "Failed to open device!" << endl;
    return -1;
  }

  // 查询设备参数
  v4l2_capability cap;
  if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1) {
    cerr << "Failed to query device capabilities!" << endl;
    close(fd);
    return -1;
  }

  // 设置摄像头参数
  v4l2_format fmt;
  fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  fmt.fmt.pix.width = 640;
  fmt.fmt.pix.height = 480;
  fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_JPEG;
  fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;

  if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -1) {
    cerr << "Failed to set device format!" << endl;
    close(fd);
    return -1;
  }

  // 请求缓冲帧
  v4l2_requestbuffers req;
  req.count = 1;
  req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  req.memory = V4L2_MEMORY_MMAP;

  if (ioctl(fd, VIDIOC_REQBUFS, &req) == -1) {
    cerr << "Failed to request buffers!" << endl;
    close(fd);
    return -1;
  }

  // 映射缓冲帧
  v4l2_buffer buf;
  buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  buf.memory = V4L2_MEMORY_MMAP;
  buf.index = 0;

  if (ioctl(fd, VIDIOC_QUERYBUF, &buf) == -1) {
    cerr << "Failed to query buffer!" << endl;
    close(fd);
    return -1;
  }

  void* ptr = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
  if (ptr == MAP_FAILED) {
    cerr << "Failed to map buffer!" << endl;
    close(fd);
    return -1;
  }

  // 开始捕获图像
  if (ioctl(fd, VIDIOC_STREAMON, &buf.type) == -1) {
    cerr << "Failed to start streaming!" << endl;
    close(fd);
    return -1;
  }

  // 获取图像数据
  if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
    cerr << "Failed to enqueue buffer!" << endl;
    close(fd);
    return -1;
  }

  fd_set fds;
  FD_ZERO(&fds);
  FD_SET(fd, &fds);

  timeval tv;
  tv.tv_sec = 2;
  tv.tv_usec = 0;

  // 等待数据准备就绪
  int r = select(fd + 1, &fds, NULL, NULL, &tv);
  if (r == -1) {
    cerr << "Failed to wait for data!" << endl;
    close(fd);
    return -1;
  } else if (r == 0) {
    cerr << "Timeout waiting for data!" << endl;
    close(fd);
    return -1;
  }

  // 获取图像数据
  if (ioctl(fd, VIDIOC_DQBUF, &buf) == -1) {
    cerr << "Failed to dequeue buffer!" << endl;
    close(fd);
    return -1;
  }

  // 写入图像文件
  string filename = "image.jpg";
  ofstream ofs(filename, ios::binary);
  ofs.write((const char*)ptr, buf.bytesused);
  ofs.close();
  cout << "Image saved to " << filename << endl;

  // 停止捕获图像
  if (ioctl(fd, VIDIOC_STREAMOFF, &buf.type) == -1) {
    cerr << "Failed to stop streaming!" << endl;
    close(fd);
    return -1;
  }

  // 关闭设备
  close(fd);

  return 0;
}

这个代码示例将从 `/dev/video0` 设备读取摄像头的图像数据，并将其保存为 JPEG 格式的文件。你可以根据需要更改摄像头设备名称以及图像的宽度、高度和格式。

注意，这个代码示例只是一个基本的框架，你需要根据自己的需求对其进行修改和扩展。例如，你可能需要添加对摄像头参数的查询、设置和调整，或者添加对多个缓冲帧的支持。