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/* Big thanks to https://gist.github.com/maxlapshin/1253534 for most of the V4L2 stuff */
#include <stdio.h> //
#include <stdlib.h> //
#include <sys/ioctl.h> // interface with V4L2
#include <getopt.h> // get command line options
#include <fcntl.h> // open() function
#include <errno.h> // Error handling
#include <sys/mman.h> // mmap() function
#include <unistd.h> // sleep() function
#include <stdint.h> // uint8_t for the buffer
#include <string.h> // memset() function
#include <linux/videodev2.h> // The main V4L2 header (camera api functions)
#define VDEV "/dev/video0" // The video device you want to capture from
#define PXWIDTH 320 // Capture resolution, change this to match the output
#define PXHEIGHT 240 // of `v4l2-ctl -d <n> --all | grep Bounds` if it fails
// Global variables
uint8_t *buffer;
int totalpixels = PXWIDTH*PXHEIGHT, minbright = 1, time = 5;
float multiplier = 1;
static int oneshot_flag, help_flag;
// find out if we have any screw-ups while doing ioctl()
static int xioctl(int fd, int request, void *arg) {
int r;
do r = ioctl(fd, request, arg);
while (-1 == r && EINTR == errno);
return r;
}
// Get brightness of image from YUYV buffer
int getbrightness() {
int returnval, bignumber = 0;
for (int i = 0; i < totalpixels; i+=2) {
bignumber+=buffer[i];
}
returnval = (bignumber/totalpixels - 8 + minbright) * multiplier;
if (returnval <= 0) {
returnval = minbright;
}
//printf("%i\n", returnval); // For testing
return returnval;
}
void help() {
printf("\
usage: xbacklight-auto [options]\n\
options:\n\
-h | --help display help\n\
-m | --minimum minimum possible brightness\n\
-o | --oneshot sample once and exit\n\
-t | --time time between samples\n\
-x | --multiplier multiplier on the final brightness\n\
");
}
int main(int argc, char **argv) {
char cmd[64];
int c, brightness, offset = 0;
FILE *xstatecmd;
float xstate1, xstate2;
// Get options
for (;;) {
static struct option long_options[] =
{
{"help" , no_argument, &help_flag , 1},
{"oneshot" , no_argument, &oneshot_flag, 1},
{"minimum" , required_argument, 0, 'm'},
{"multiplier" , required_argument, 0, 'x'},
{"time" , required_argument, 0, 't'},
};
int option_index = 0;
c = getopt_long(argc, argv, "m:t:x:oh", long_options, &option_index);
if (c == -1) { break; }
switch(c) {
case 0: //do nothing
break;
case 't': // time
time = atoi(optarg);
break;
case 'x': //multiplier
multiplier *=atof(optarg);
break;
case 'm': //minbright
minbright = atoi(optarg);
break;
case 'o': // oneshot
oneshot_flag = 1;
break;
case 'h': // help
help_flag = 1;
break;
default:
abort();
}
}
if (help_flag == 1) {
help();
return 0;
}
if (oneshot_flag == 1) {
time = 0;
}
// Open the video device
int fd = open(VDEV, O_RDWR);
if (fd == -1) {
perror("Error opening device");
return 1;
}
// Get the capabilities of the camera
struct v4l2_capability caps;
if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &caps)) {
perror("Querying capabilities");
return 1;
}
// Set the capture format
struct v4l2_format fmt = {0};
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = PXWIDTH;
fmt.fmt.pix.height = PXHEIGHT;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
fmt.fmt.pix.field = V4L2_FIELD_NONE;
if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt)) {
perror("Error setting pixel format");
return 1;
}
// Request buffer
struct v4l2_requestbuffers req = {0};
req.count = 1;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req))
{
perror("Requesting buffer");
return 1;
}
// main loop
do {
// Query buffer
struct v4l2_buffer buf;
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = 0;
if(-1 == xioctl(fd, VIDIOC_QBUF, &buf)) {
perror("Querying buffer");
return 1;
}
buffer = mmap (NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
// Consoom frame and get excited for next frame
if (-1 == xioctl(fd, VIDIOC_STREAMON, &buf.type)) {
perror("Starting capture");
return 1;
}
fd_set fds;
FD_ZERO(&fds);
FD_SET(fd, &fds);
struct timeval tv = {0};
tv.tv_sec = 2;
int r = select(fd+1, &fds, NULL, NULL, &tv);
if(-1 == r) {
perror("Waiting for frame");
return 1;
}
if(-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) {
perror("Retrieving frame");
return 1;
}
if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &buf.type)) {
perror("Stopping capture");
}
/*TODO These are sufficient for now, but I want to add a more
native method for changing the xbacklight state later*/
brightness = getbrightness() + offset;
sprintf(cmd, "xbacklight -set %i%%", brightness);
system(cmd);
// Sample xbacklight state
xstatecmd = popen("xbacklight -get", "r");
fscanf(xstatecmd, "%f", &xstate1);
sleep(time);
// Sample state again and diff to get manual input
xstatecmd = popen("xbacklight -get", "r");
fscanf(xstatecmd, "%f", &xstate2);
offset = xstate2 - xstate1 + offset;
}
while (oneshot_flag != 1);
// Never gets used lmao
return 0;
}
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