framebuffer.c

基于framebuffer的图形显示程序

#include <unistd.h> 
#include <stdio.h> 
#include <fcntl.h> 
#include <linux/fb.h> 
#include <sys/mman.h> 

int main () { 
int fp=0; 
struct fb_var_screeninfo vinfo; 
struct fb_fix_screeninfo finfo; 
long screensize=0; 
char *fbp = 0; 
int x = 0, y = 0; 
long location = 0; 
fp = open ("/dev/fb0",O_RDWR); 

if (fp < 0){ 
printf("Error : Can not open framebuffer device\n"); 
exit(1); 
} 

if (ioctl(fp,FBIOGET_FSCREENINFO,&finfo)){ 
printf("Error reading fixed information\n"); 
exit(2); 
} 

if (ioctl(fp,FBIOGET_VSCREENINFO,&vinfo)){ 
printf("Error reading variable information\n"); 
exit(3); 
} 

screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8; 
/*这就是把fp所指的文件中从开始到screensize大小的内容给映射出来，得到一个指向这块空间的指针*/ 
fbp =(char *) mmap (0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fp,0); 
if ((int) fbp == -1) 
{ 
printf ("Error: failed to map framebuffer device to memory.\n"); 
exit (4); 
} 
/*这是你想画的点的位置坐标,(0，0)点在屏幕左上角*/ 
x = 100; 
y = 100; 
location = x * (vinfo.bits_per_pixel / 8) + y * finfo.line_length; 

*(fbp + location) = 100; /* 蓝色的色深 */ /*直接赋值来改变屏幕上某点的颜色*/ 
*(fbp + location + 1) = 15; /* 绿色的色深*/ 
*(fbp + location + 2) = 200; /* 红色的色深*/ 
*(fbp + location + 3) = 0; /* 是否透明*/ 
munmap (fbp, screensize); /*解除映射*/ 
close (fp); /*关闭文件*/ 
return 0; 

}