ubuntu下framebuffer的操作例程

下面是个小Demo

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

int main()
{
	int fbfd = 0;
	struct fb_var_screeninfo vinfo;
	unsigned long screensize = 0;
	char *fbp = 0;
	int x = 0, y = 0;
	int i = 0;
	// Open the file for reading and writing
	fbfd = open("/dev/fb0", O_RDWR);
	if (!fbfd) {
	printf("Error: cannot open framebuffer device.
");
	exit(1);
	}
	printf("The framebuffer device was opened successfully.
");
	// Get variable screen information
	if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
	printf("Error reading variable information.
");
	exit(1);
	}
	printf("%dx%d, %dbpp
", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
	if (vinfo.bits_per_pixel != 32) {
	printf("Error: not supported bits_per_pixel, it only supports 32 bit color
");
	exit(1);
	}
	// Figure out the size of the screen in bytes
	screensize = vinfo.xres * vinfo.yres * 2;
	// 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.
");
	exit(4);
	}
	printf("The framebuffer device was mapped to memory successfully.
");
	// Draw 3 rect with graduated RED/GREEN/BLUE
	for (i = 0; i < 3; i++) {
		for (y = i * (vinfo.yres / 3); y < (i + 1) * (vinfo.yres / 3); y++) {
			for (x = 0; x < vinfo.xres; x++) {
			long location = x * 4 + y * vinfo.xres * 4;
			int r = 0, g = 0, b = 0;
			unsigned int rgb;
			if (i == 0)
			r = (x * 255) / vinfo.xres;
			if (i == 1)
			g = (x * 255) / vinfo.xres;
			if (i == 2)
			b = (x * 255) / vinfo.xres;
			rgb = (r << 24) | (g << 16) | (b << 8) ;
			*((unsigned int *)(fbp + location)) = rgb;
			}
		}
	}
	munmap(fbp, screensize);
	close(fbfd);
	return 0;
}