fbsnapshot, 无敌截图玩具

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <stdio.h>
#include <linux/fb.h>
#include <gd.h>

int main(void){
 int fbfd;
 int i;
 struct fb_var_screeninfo vinfo;
 struct fb_fix_screeninfo finfo;
 int screensize;
 int bp;
 unsigned char* fbp;
 gdImagePtr im;
 FILE *out;

fbfd = open("/dev/fb", O_RDWR);
 ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo);
 ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo);
 bp = vinfo.bits_per_pixel/8;
 screensize = vinfo.xres*vinfo.yres;
 fbp = mmap(NULL, screensize*bp, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
 printf("%ux%u@%ubpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
 im = gdImageCreateTrueColor(vinfo.xres, vinfo.yres);
 out = fopen("fbsnapshot.png", "wb");
 switch(bp){
 case 4:
 for(i = 0; i < screensize; ++i){
 gdImageSetPixel(im, i%vinfo.xres, i/vinfo.xres,
 gdImageColorAllocate(im,
 fbp[4*i + 2],
 fbp[4*i + 1],
 fbp[4*i + 0]));
 }
 break;
 default:
 printf("Unhandled bpp %d\n", bp);
 }
 gdImagePng(im, out);
 fclose(out);
 gdImageDestroy(im);
}

fbsnapshot : fbsnapshot.c
 gcc $(gdlib-config --cflags) $(gdlib-config --libs) -lgd $< -o $@