目前根据自己对linux中framebuffer的了解写了如下的代码:
下面是用到的一些文件,在linux下编译通过,显示图形效果。
效果:主要代码在fb.c中,在显卡x,y=(1100,100)出显示x0,y0=(130,150)大小的颜色,再在x0,y0的坐标基础上添加红色图像,如代码所所示。
main.c
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <time.h>
#include <sys/mman.h>
#include"fb.h"
int main()
{
init_fb();//init framebuffer
return 0;
}
fb.c
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <time.h>
#include <sys/mman.h>
#include"fb.h"
color_t color={0,0,150,100}; //the color of background
color_t color1={0,255,0,0}; //in window red
int init_fb()
{
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;
long int location1 = 0;
fbfd = open("/dev/fb0", O_RDWR); // Open the file for reading and writing
if (!fbfd)
{
printf("Error: cannot open framebuffer device.\n");
exit(0);
}
printf("The framebuffer device was opened successfully.\n");
// Get fixed screen information
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo))
{
printf("Error reading fixed information.\n");
exit(0);
}
// Get variable screen information
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo))
{
printf("Error reading variable information.\n");
exit(0);
}
printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
// Figure out the size of the screen in bytes
screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
printf("screensize is %ldKB\n",screensize/1024);
// Map the device to memory
fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
if((int)fbp == -1)
{
printf("Error: failed to map framebuffer device to memory.\n");
exit(0);
}
printf("The framebuffer device was mapped to memory successfully.\n");
for (x = 0; x < DISPLAY_WIDE; x++)
for (y = 0; y < DISPLAY_HIGH; y++)
{
location = (x+1100+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +(y+100+vinfo.yoffset) * finfo.line_length;
//if (vinfo.bits_per_pixel == 32)
*(fbp + location + 3) = color.t;// No transparency
*(fbp + location + 2) = color.r;// A red
*(fbp + location + 1) = color.g;// A green
*(fbp + location) = color.b; // Some blue
}
/*
function:in window display red
author :sjmp
time :2012.06.02
*/
for (x = 0; x < DISPLAY_WIDE-10; x++)
for (y = 0; y < DISPLAY_HIGH-10; y++)
{
location1 = (x+5+(1100+vinfo.xoffset)) * (vinfo.bits_per_pixel/8) +(y+(5+100+vinfo.yoffset)) * finfo.line_length;
*(fbp + location1 + 3) = color1.t;
*(fbp + location1 + 2) = color1.r;
*(fbp + location1 + 1) = color1.g;
*(fbp + location1) = color1.b;
}
munmap(fbp, screensize);
return 0;
close(fbfd);
}
fb.h
#ifndef FBI_H_
#define FBI_H_
#define DISPLAY_WIDE 130 //display wide
#define DISPLAY_HIGH 150 //display high
typedef struct
{
int t;
int r;
int g;
int b;
} color_t;
int init_fb();
#endif
Makefile
%.o : %.c
@gcc -Wall -c $< -o $@
OBJS= main.o fb.o //only this need change
all: $(OBJS)
@gcc $(OBJS) -o fb
@strip fb //put 'fb ' in the first place
clean:
@rm -f *.o
@rm -f *.c~
@rm -f fb