写一个Linux 上的c程序,要求调用v4l2 接口拍摄一张照片并保存
时间: 2024-01-24 13:17:04 浏览: 26
下面是一个简单的C程序,它使用v4l2接口从Linux摄像头中捕获一张照片并将其保存到指定的文件中:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <linux/videodev2.h>
#define WIDTH 640
#define HEIGHT 480
int main(int argc, char **argv)
{
int fd;
struct v4l2_capability cap;
struct v4l2_format format;
struct v4l2_requestbuffers reqbuf;
struct v4l2_buffer buf;
void *buffer;
int n_buffers;
// 打开摄像头设备
fd = open("/dev/video0", O_RDWR);
if (fd == -1) {
printf("Failed to open /dev/video0: %s\n", strerror(errno));
return -1;
}
// 查询设备属性
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1) {
printf("Failed to query device: %s\n", strerror(errno));
close(fd);
return -1;
}
// 设置视频格式
memset(&format, 0, sizeof(format));
format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
format.fmt.pix.width = WIDTH;
format.fmt.pix.height = HEIGHT;
format.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;
if (ioctl(fd, VIDIOC_S_FMT, &format) == -1) {
printf("Failed to set video format: %s\n", strerror(errno));
close(fd);
return -1;
}
// 请求缓冲区
memset(&reqbuf, 0, sizeof(reqbuf));
reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
reqbuf.memory = V4L2_MEMORY_MMAP;
reqbuf.count = 1;
if (ioctl(fd, VIDIOC_REQBUFS, &reqbuf) == -1) {
printf("Failed to request buffers: %s\n", strerror(errno));
close(fd);
return -1;
}
// 映射缓冲区
buffer = mmap(NULL, reqbuf.count * format.fmt.pix.sizeimage,
PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (buffer == MAP_FAILED) {
printf("Failed to map buffers: %s\n", strerror(errno));
close(fd);
return -1;
}
// 将缓冲区添加到队列中
memset(&buf, 0, sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = 0;
if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
printf("Failed to add buffer to queue: %s\n", strerror(errno));
close(fd);
return -1;
}
// 开始捕获
if (ioctl(fd, VIDIOC_STREAMON, &buf.type) == -1) {
printf("Failed to start capture: %s\n", strerror(errno));
close(fd);
return -1;
}
// 获取图像数据
if (ioctl(fd, VIDIOC_DQBUF, &buf) == -1) {
printf("Failed to get buffer from queue: %s\n", strerror(errno));
close(fd);
return -1;
}
// 保存图像数据到文件
FILE *file = fopen(argv[1], "w");
fwrite(buffer, buf.bytesused, 1, file);
fclose(file);
// 停止捕获
if (ioctl(fd, VIDIOC_STREAMOFF, &buf.type) == -1) {
printf("Failed to stop capture: %s\n", strerror(errno));
close(fd);
return -1;
}
// 解除映射
if (munmap(buffer, reqbuf.count * format.fmt.pix.sizeimage) == -1) {
printf("Failed to unmap buffers: %s\n", strerror(errno));
close(fd);
return -1;
}
// 关闭设备
close(fd);
return 0;
}
```
该程序使用v4l2接口从摄像头中捕获一张图片,并将其保存到指定的文件中。可以使用以下命令编译并运行该程序:
```bash
$ gcc -o capture capture.c
$ ./capture image.jpg
```
其中,image.jpg是要保存的文件名。
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