linux应用编程--显示bmp图片

#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 char blue;  
	unsigned char green;  
	unsigned char red;  
//	unsigned char 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.offset, vinfo.green.offset, vinfo.blue.offset ); 
	printf("R:%d,G:%d,B:%d \n", vinfo.red.length, vinfo.green.length, vinfo.blue.length );  
  
	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);  
	}  
 
	//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;  
  
	fp = fopen( "timg.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;	
		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)=0;  
		line_x++;  
		if (line_x == InfoHead.ciWidth)  
		{  
			line_x = 0;  
			line_y++;  
			if(line_y == InfoHead.ciHeight)  
				break;	
		}  
	}  
	fclose(fp);  
	return(0);  
}