How do I capture an image with my webcam using C++ and save it to disk? I cannot use OPENCV due to hardware problems. The usb webcam does work with other programs such as mplayer, cheese, gpicview, ffmpeg, etc.
I heard V4L is capable of doing this, but does it have any C++ libraries? Can anybody show me a C++ example on how to do this?
It is quite easy, you can do read
on a videodevice, after you have activated some ioctls to get the cam under your control.
You can use v4l2 for this job. You do this in those steps:
Here is a implementation I use for this job. It will set the camera to capture a video in 320x240 Pixel, but you can read the resolutions, the camera is capable of from the v4l2_capability
structure.
Also I haven't tested the code on different Cameras than my PS2 EyeToy, but it is mostly taken from a sample program named qv4l2 (you can get it from here). This program should solve all other issues you usually see there.
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h> /* low-level i/o */
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
static int xioctl(int fh, int request, void *arg)
{
int r;
do {
r = ioctl(fh, request, arg);
} while (-1 == r && EINTR == errno);
return r;
}
int allocCamera(const char* file)
{
struct v4l2_capability cap;
struct v4l2_crop crop;
struct v4l2_format fmt;
int camera_fd = open(file, O_RDONLY);
if (-1 == xioctl (camera_fd, VIDIOC_QUERYCAP, &cap)) {
if (EINVAL == errno) {
fprintf (stderr, "%s is no V4L2 device\n", file);
exit (EXIT_FAILURE);
} else {
printf("\nError in ioctl VIDIOC_QUERYCAP\n\n");
exit(0);
}
}
if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
fprintf (stderr, "%s is no video capture device\n", file);
exit (EXIT_FAILURE);
}
if (!(cap.capabilities & V4L2_CAP_READWRITE)) {
fprintf (stderr, "%s does not support read i/o\n", file);
exit (EXIT_FAILURE);
}
memset(&fmt, 0, sizeof(fmt));
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = 320;
fmt.fmt.pix.height = 240;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
if (-1 == xioctl(camera_fd, VIDIOC_S_FMT, &fmt)) {
printf("VIDIOC_S_FMT");
}
return camera_fd;
}
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