/**
* get-luminosity — Determine how bright it is in your room
* Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "linearise.h"
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <stropts.h>
#include <linux/fb.h>
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
int main()
{
auto struct fb_var_screeninfo var_info;
long width;
long height;
long y;
auto int fd;
auto const char* restrict mem;
register double grand_sum = 0;
double inv_width;
if (fd = open("/dev/fb0", O_RDONLY), fd == -1)
return perror("get-luminosity::framebuffer: open: /dev/fb0"), close(fd), 1;
if (ioctl(fd, (unsigned long)FBIOGET_VSCREENINFO, &var_info))
return perror("get-luminosity::framebuffer: ioctl"), close(fd), 1;
width = var_info.xres;
height = var_info.yres;
inv_width = 1 / (double)width;
posix_fadvise(fd, 0, (size_t)(width * height * 4),
POSIX_FADV_SEQUENTIAL | POSIX_FADV_NOREUSE | POSIX_FADV_WILLNEED);
mem = mmap(NULL, (size_t)(width * height * 4), PROT_READ, MAP_SHARED, fd, (off_t)0);
if (mem == MAP_FAILED)
return perror("get-luminosity::framebuffer: mmap"), close(fd), 1;
for (y = 0; y < height; y++)
{
register const int32_t* restrict linemem = (const int32_t*)(mem + y * width * 4);
register const int32_t* restrict end = linemem + width;
double sum = 0;
while (linemem != end)
{
int32_t value = *linemem++;
sum += linearise(value, 0) + linearise(value, 1) + linearise(value, 2);
}
grand_sum += sum * inv_width;
}
grand_sum /= (double)(height * 3);
fprintf(stderr, "%lf\n", (double)grand_sum);
fflush(stdout);
close(fd);
return 0;
}
