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| #include <stdlib.h> #include <unistd.h> #include <stdio.h> #include <fcntl.h> #include <linux/fb.h> #include <sys/mman.h> #include <sys/ioctl.h>
int main() { int fbfd = 0; struct fb_var_screeninfo vinfo; struct fb_fix_screeninfo finfo; long int screensize = 0; char *fbp = 0; int x = 0, y = 0; long int location = 0;
fbfd = open("/dev/fb0", O_RDWR); if (fbfd == -1) { perror("Error: cannot open framebuffer device"); exit(1); } printf("The framebuffer device was opened successfully.\n");
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) { perror("Error reading fixed information"); exit(2); }
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) { perror("Error reading variable information"); exit(3); }
printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0); if ((int)fbp == -1) { perror("Error: failed to map framebuffer device to memory"); exit(4); } printf("The framebuffer device was mapped to memory successfully.\n");
x = 300; y = 100;
while (1) { for (y = 100; y < 300; y++) { for (x = 100; x < 300; x++) { location = (x + vinfo.xoffset) * (vinfo.bits_per_pixel / 8) + (y + vinfo.yoffset) * finfo.line_length;
if (vinfo.bits_per_pixel == 32) { *(fbp + location) = 100; *(fbp + location + 1) = 15 + (x - 100) / 2; *(fbp + location + 2) = 200 - (y - 100) / 5; *(fbp + location + 3) = 0; } else { int b = 10; int g = (x - 100) / 6; int r = 31 - (y - 100) / 16; unsigned short int t = r << 11 | g << 5 | b; *((unsigned short int *)(fbp + location)) = t; } } } } munmap(fbp, screensize); close(fbfd); return 0; }
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