V4L2摄像头获取单幅图片测试程序

#根据网上常见的一个测试程序修改而来 by rockie cheng
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include <getopt.h>           

#include <fcntl.h>             
#include <unistd.h>
#include <errno.h>
#include <malloc.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>

#include <asm/types.h>         
#include <linux/videodev2.h>

#define CLEAR(x) memset (&(x), 0, sizeof (x))

struct buffer {
        void *                  start;
        size_t                  length;
};

static char *           dev_name        = "/dev/video0";
static int              fd              = -1;
struct buffer *         buffers         = NULL;

FILE *file_fd;
static unsigned long file_length;
static unsigned char *file_name;

int main (int argc,char ** argv)
{
struct v4l2_capability cap; 
struct v4l2_format fmt;

file_fd = fopen("test.jpg", "w");

fd = open (dev_name, O_RDWR /* required */ | O_NONBLOCK, 0);

ioctl (fd, VIDIOC_QUERYCAP, &cap);

CLEAR (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_YUYV;
fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;
ioctl (fd, VIDIOC_S_FMT, &fmt);

file_length = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;

buffers = calloc (1, sizeof (*buffers));

buffers[0].length = file_length;
buffers[0].start = malloc (file_length);

for (;;) 
{
   fd_set fds;
   struct timeval tv;
   int r;

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

   /* Timeout. */
   tv.tv_sec = 3;
   tv.tv_usec = 0;

   r = select (fd + 1, &fds, NULL, NULL, &tv);

   if (-1 == r) {
    if (EINTR == errno)
     continue;
    printf ("select");
                        }

   if (0 == r) {
    fprintf (stderr, "select timeout\n");
    exit (EXIT_FAILURE);
                        }

   if (read (fd, buffers[0].start, buffers[0].length))
   break;
}

fwrite(buffers[0].start, buffers[0].length, 1, file_fd);

free (buffers[0].start);
close (fd);
fclose (file_fd);
exit (EXIT_SUCCESS);
return 0;
}