framebuffer.c

可以在linux下显示显示图片的小程序。

/*#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>

#include <stdio.h>
#include <stdlib.h>

#include "framebuffer.h"
*/
#define FB_DEVICE "/dev/fb0"

int closeFrameBufferDevice(int fbFd)
{
	int ret;

	if(fbFd < 0)
		return -1;

	ret = close(fbFd);

	return ret;
} // end of closeFrameBufferDevice

int openFrameBufferDevice(void)
{
	int fbFd;
	
	fbFd = open(FB_DEVICE, O_RDWR);
	if(fbFd < 0)
	{
		fprintf(stderr, "Line %d :open framebuffer device error !\n", __LINE__);
		return -1;
	}
	return fbFd;
}

int getFrameBufferInfo(int fbFd, struct fb_var_screeninfo * vsinfo)
{
	int ret;

	ret = ioctl(fbFd, FBIOGET_VSCREENINFO, vsinfo);
	if(ret < 0)
	{
		fprintf(stderr, "Line %d :read FBIOGET_VSCREENINFO Error !\n", __LINE__);
		return -1;
	}
#ifdef DEBUG
	fprintf(stdout, "bits = %u\n", 
			vsinfo->bits_per_pixel);
	fprintf(stdout, "xres = %u\n", 
			vsinfo->xres);
	fprintf(stdout, "yres = %u\n", 
			vsinfo->yres);
#endif //DEBUG

	return 0;
}

int frameBufferOffset(struct fb_var_screeninfo *vsinfo, int x, int y)
{
	// (x, y)offset  (x * screen_width + y) * color_bits / 8
	return (y * vsinfo->xres + x) * vsinfo->bits_per_pixel / 8;
} // end of frameBufferOffset
#ifndef MMAP
int readPixelToFrameBuffer(int fbFd, int offset, rgb *color)
{
	int ret;

	ret = lseek(fbFd, offset, SEEK_SET);
	if(ret == -1)
	{
		fprintf(stderr, "Line %d :seek to offset : %d error !\n", __LINE__, offset);
		return -1;
	}
	ret = read(fbFd, color, sizeof(rgb));
	if(ret != sizeof(rgb))
	{
		fprintf(stderr, "Line %d :write one pixel to framebuffer error !\n", __LINE__);
		return -1;
	}
	return 0;
}

int writePixelToFrameBuffer(int fbFd, int offset, rgb *color)
{
	int ret;

	ret = lseek(fbFd, offset, SEEK_SET);
	if(ret == -1)
	{
		fprintf(stderr, "Line %d :seek to offset : %d error !\n", __LINE__, offset);
		perror("");
		return -1;
	}
	ret = write(fbFd, color, sizeof(rgb));
	if(ret != sizeof(rgb))
	{
		fprintf(stderr, "Line %d :write one pixel to framebuffer error !\n", __LINE__);
		return -1;
	}
	return 0;
}
#else
unsigned short *frameBufferMap(int fbFd, struct fb_var_screeninfo *vsinfo)
{
	unsigned short * p;

	p = (unsigned short *)mmap(NULL, 
					vsinfo->xres * vsinfo->yres * vsinfo->bits_per_pixel / 8,
					PROT_READ | PROT_WRITE,
					MAP_SHARED,
					fbFd,
					0);
	if(! p)
		fprintf(stderr, "LINE: %d, mmap failed !\n", __LINE__);
	
	return p;
}

int frameBufferUnmap(unsigned short * p, struct fb_var_screeninfo *vsinfo)
{
	int ret;
	
	if(! p)
	{
		fprintf(stderr, "LINE: %d, NULL, cannot munmap !\n", __LINE__);
		return -1;
	}
	ret = munmap(p, vsinfo->xres * vsinfo->yres * vsinfo->bits_per_pixel / 8);
	if(ret < 0)
		fprintf(stderr, "LINE: %d, munmap failed !\n", __LINE__);

	return ret;
}
#endif //MMAP
#ifdef DEBUG
int main()
{
	int fbFd, ret, i, j;
	struct fb_var_screeninfo vsinfo;
#ifdef MMAP
	unsigned short *p;
#endif //MMAP
	rgb color;

//设置RGB565颜色为红色
	color._c565.r = 255 >> 3;
	color._c565.g = 0;
	color._c565.b = 0;
	
	fbFd = openFrameBufferDevice();
	if(fbFd < 0) exit(fbFd);
	
	ret = getFrameBufferInfo(fbFd, &vsinfo);
	if(ret < 0)
	{
		closeFrameBufferDevice(fbFd);
		exit(ret);
	}
#ifdef MMAP
	p = frameBufferMap(fbFd, &vsinfo);
	if(! p) exit(-1);
#endif //MMAP
//	for(i = 0; i < vsinfo.xres; i++)
	for(i = 100; i < 611; i++)
	{
		color._c565.r++;
		color._c565.g++;
		color._c565.b++;
		for(j = 100; j < 400; j++)
		{
#ifdef MMAP
			*(p + (vsinfo.xres * j) + i) = color._c16;
#else
			ret = writePixelToFrameBuffer(fbFd, 
				frameBufferOffset(&vsinfo, i, j), &color);
			if(ret < 0)
			{
				closeFrameBufferDevice(fbFd);
				exit(ret);
			}
#endif //MMAP
		}
	}
#ifdef MMAP
	frameBufferUnmap(p, &vsinfo);
#endif // MMAP
	closeFrameBufferDevice(fbFd);
	

	return EXIT_SUCCESS;
}
#endif //DEBUG