FrameBuffer系列 之 显示图片



摘自：http://blog.csdn.net/luxiaoxun/article/details/7622988

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>

//14byte文件头
typedef struct
{
	char cfType[2];//文件类型，"BM"(0x4D42)
	long cfSize;//文件大小（字节）
	long cfReserved;//保留，值为0
	long cfoffBits;//数据区相对于文件头的偏移量（字节）
}__attribute__((packed)) BITMAPFILEHEADER;
//__attribute__((packed))的作用是告诉编译器取消结构在编译过程中的优化对齐

//40byte信息头
typedef struct
{
	char ciSize[4];//BITMAPFILEHEADER所占的字节数
	long ciWidth;//宽度
	long ciHeight;//高度
	char ciPlanes[2];//目标设备的位平面数，值为1
	int ciBitCount;//每个像素的位数
	char ciCompress[4];//压缩说明
	char ciSizeImage[4];//用字节表示的图像大小，该数据必须是4的倍数
	char ciXPelsPerMeter[4];//目标设备的水平像素数/米
	char ciYPelsPerMeter[4];//目标设备的垂直像素数/米
	char ciClrUsed[4]; //位图使用调色板的颜色数
	char ciClrImportant[4]; //指定重要的颜色数，当该域的值等于颜色数时（或者等于0时），表示所有颜色都一样重要
}__attribute__((packed)) BITMAPINFOHEADER;

typedef struct
{
	unsigned short blue;
	unsigned short green;
	unsigned short red;
	unsigned short reserved;
}__attribute__((packed)) PIXEL;//颜色模式RGB

BITMAPFILEHEADER FileHead;
BITMAPINFOHEADER InfoHead;

static char *fbp = 0;
static int xres = 0;
static int yres = 0;
static int bits_per_pixel = 0;

int show_bmp();

int main ( int argc, char *argv[] )
{
	int fbfd = 0;
	struct fb_var_screeninfo vinfo;
	struct fb_fix_screeninfo finfo;
	long int screensize = 0;
	struct fb_bitfield red;
	struct fb_bitfield green;
	struct fb_bitfield blue;

	//打开显示设备
	fbfd = open("/dev/fb0", O_RDWR);
	if (!fbfd)
	{
		printf("Error: cannot open framebuffer device.\n");
		exit(1);
	}

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

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

	printf("R:%d,G:%d,B:%d \n", vinfo.red, vinfo.green, vinfo.blue );

	printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel );
	xres = vinfo.xres;
	yres = vinfo.yres;
	bits_per_pixel = vinfo.bits_per_pixel;

	//计算屏幕的总大小（字节）
	screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
	printf("screensize=%d byte\n",screensize);

	//对象映射
	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(4);
	}

	printf("sizeof file header=%d\n", sizeof(BITMAPFILEHEADER));

	printf("into show_bmp function\n");

	//显示图像
	show_bmp();

	//删除对象映射
	munmap(fbp, screensize);
	close(fbfd);
	return 0;
}

int show_bmp()
{
	FILE *fp;
	int rc;
	int line_x, line_y;
	long int location = 0, BytesPerLine = 0;
	char tmp[1024*10];

	fp = fopen( "./niu.bmp", "rb" );
	if (fp == NULL)
	{
		return( -1 );
	}

	rc = fread( &FileHead, sizeof(BITMAPFILEHEADER),1, fp );
	if ( rc != 1)
	{
		printf("read header error!\n");
		fclose( fp );
		return( -2 );
	}

	//检测是否是bmp图像
	if (memcmp(FileHead.cfType, "BM", 2) != 0)
	{
		printf("it's not a BMP file\n");
		fclose( fp );
		return( -3 );
	}

	rc = fread( (char *)&InfoHead, sizeof(BITMAPINFOHEADER),1, fp );
	if ( rc != 1)
	{
		printf("read infoheader error!\n");
		fclose( fp );
		return( -4 );
	}

	//跳转的数据区
	fseek(fp, FileHead.cfoffBits, SEEK_SET);
	//每行字节数
	BytesPerLine = (InfoHead.ciWidth * InfoHead.ciBitCount + 31) / 32 * 4;

	line_x = line_y = 0;
	//向framebuffer中写BMP图片
	while(!feof(fp))
	{
		PIXEL pix;
		unsigned short int tmp;
		rc = fread( (char *)&pix, 1, sizeof(PIXEL), fp);
		if (rc != sizeof(PIXEL))
			break;
		location = line_x * bits_per_pixel / 8 + (InfoHead.ciHeight - line_y - 1) * xres * bits_per_pixel / 8;

		//显示每一个像素
		*(fbp + location + 0)=pix.blue;
		*(fbp + location + 1)=pix.green;
		*(fbp + location + 2)=pix.red;
		*(fbp + location + 3)=pix.reserved;

		line_x++;
		if (line_x == InfoHead.ciWidth )
		{
			line_x = 0;
			line_y++;
			if(line_y == InfoHead.ciHeight)
				break;
		}
	}
	fclose( fp );
	return( 0 );
}

注意：上面的程序只在framebuffer上显示图片，却没有删除刷新屏幕，可以使用下面的命令恢复屏幕

保存屏幕信息：dd if=/dev/fb0 of=fbfile 或： cp /dev/fb0 fbfile

恢复屏幕信息：dd if=fbfile of=/dev/fb0 或： cat fbfile > /dev/fb0

FrameBuffer系列 之 介绍

http://blog.csdn.net/younger_china/article/details/14479859

FrameBuffer系列 之 相关结构与结构体

http://blog.csdn.net/younger_china/article/details/14480967

FrameBuffer系列 之 简单编程

http://blog.csdn.net/younger_china/article/details/14236251

FrameBuffer系列之显示图片

http://blog.csdn.net/younger_china/article/details/14481755

FrameBuffer系列之一点资源

http://blog.csdn.net/younger_china/article/details/14482049