v4l2写一个方法,该方法一次拍摄一张图片,可以多次使用该方法,生成的代码加换行符
时间: 2024-06-08 11:10:41 浏览: 9
以下是使用v4l2进行一次拍摄的方法:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
#define CAMERA_DEVICE "/dev/video0"
#define CAPTURE_FILE "image.jpg"
#define IMAGE_WIDTH 640
#define IMAGE_HEIGHT 480
int main()
{
int fd;
struct v4l2_capability cap;
struct v4l2_format fmt;
struct v4l2_requestbuffers req;
struct v4l2_buffer buf;
void *buffer;
// 打开视频设备文件
if ((fd = open(CAMERA_DEVICE, O_RDWR)) == -1) {
perror("Cannot open video device");
return EXIT_FAILURE;
}
// 查询设备是否支持视频采集
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1) {
perror("Cannot get device capabilities");
close(fd);
return EXIT_FAILURE;
}
// 设置视频格式
memset(&fmt, 0, sizeof(fmt));
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_MJPEG;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -1) {
perror("Cannot set video format");
close(fd);
return EXIT_FAILURE;
}
// 请求视频缓冲区
memset(&req, 0, sizeof(req));
req.count = 1;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_REQBUFS, &req) == -1) {
perror("Cannot request video buffers");
close(fd);
return EXIT_FAILURE;
}
// 映射视频缓冲区
memset(&buf, 0, sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = 0;
if (ioctl(fd, VIDIOC_QUERYBUF, &buf) == -1) {
perror("Cannot query video buffer");
close(fd);
return EXIT_FAILURE;
}
buffer = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
if (buffer == MAP_FAILED) {
perror("Cannot map video buffer");
close(fd);
return EXIT_FAILURE;
}
// 启动视频采集
if (ioctl(fd, VIDIOC_STREAMON, &buf.type) == -1) {
perror("Cannot start video stream");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
// 采集一张图片
if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
perror("Cannot enqueue video buffer");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
if (ioctl(fd, VIDIOC_DQBUF, &buf) == -1) {
perror("Cannot dequeue video buffer");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
// 将图片保存到文件
FILE *fp = fopen(CAPTURE_FILE, "wb");
if (fp == NULL) {
perror("Cannot open file for writing");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
fwrite(buffer, buf.bytesused, 1, fp);
fclose(fp);
// 停止视频采集
if (ioctl(fd, VIDIOC_STREAMOFF, &buf.type) == -1) {
perror("Cannot stop video stream");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
munmap(buffer, buf.length);
close(fd);
return EXIT_SUCCESS;
}
```
你可以将该方法放在循环中,每次调用时会拍摄一张图片并保存到文件中。加入换行符的代码如下:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
#define CAMERA_DEVICE "/dev/video0"
#define CAPTURE_FILE "image.jpg"
#define IMAGE_WIDTH 640
#define IMAGE_HEIGHT 480
int main()
{
int fd;
struct v4l2_capability cap;
struct v4l2_format fmt;
struct v4l2_requestbuffers req;
struct v4l2_buffer buf;
void *buffer;
// 打开视频设备文件
if ((fd = open(CAMERA_DEVICE, O_RDWR)) == -1) {
perror("Cannot open video device");
return EXIT_FAILURE;
}
// 查询设备是否支持视频采集
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1) {
perror("Cannot get device capabilities");
close(fd);
return EXIT_FAILURE;
}
// 设置视频格式
memset(&fmt, 0, sizeof(fmt));
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_MJPEG;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -1) {
perror("Cannot set video format");
close(fd);
return EXIT_FAILURE;
}
// 请求视频缓冲区
memset(&req, 0, sizeof(req));
req.count = 1;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_REQBUFS, &req) == -1) {
perror("Cannot request video buffers");
close(fd);
return EXIT_FAILURE;
}
// 映射视频缓冲区
memset(&buf, 0, sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = 0;
if (ioctl(fd, VIDIOC_QUERYBUF, &buf) == -1) {
perror("Cannot query video buffer");
close(fd);
return EXIT_FAILURE;
}
buffer = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
if (buffer == MAP_FAILED) {
perror("Cannot map video buffer");
close(fd);
return EXIT_FAILURE;
}
// 启动视频采集
if (ioctl(fd, VIDIOC_STREAMON, &buf.type) == -1) {
perror("Cannot start video stream");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
int i;
for (i = 0; i < 10; i++) { // 循环拍摄10张图片
// 采集一张图片
if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
perror("Cannot enqueue video buffer");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
if (ioctl(fd, VIDIOC_DQBUF, &buf) == -1) {
perror("Cannot dequeue video buffer");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
// 将图片保存到文件
FILE *fp = fopen(CAPTURE_FILE, "ab"); // 以追加模式打开文件,保证每次写入都在文件末尾
if (fp == NULL) {
perror("Cannot open file for writing");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
fwrite(buffer, buf.bytesused, 1, fp);
fprintf(fp, "\n"); // 写入换行符
fclose(fp);
}
// 停止视频采集
if (ioctl(fd, VIDIOC_STREAMOFF, &buf.type) == -1) {
perror("Cannot stop video stream");
munmap(buffer, buf.length);
close(fd);
return EXIT_FAILURE;
}
munmap(buffer, buf.length);
close(fd);
return EXIT_SUCCESS;
}
```
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