Linux C语言解析并显示.bmp格式图片

/************************* *bmp.h文件 *************************/ #ifndef __BMP_H__
#define __BMP_H__ #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> //文件头结构体
typedef struct
{
unsigned char bfType[]; //文件类型
unsigned long bfSize; //位图大小
unsigned short bfReserved1; //位0
unsigned short bfReserved2; //位0
unsigned long bfOffBits; //到数据偏移量
} __attribute__((packed)) BitMapFileHeader; //使编译器不优化，其大小为14字节 //信息头结构体
typedef struct
{
unsigned long biSize; // BitMapFileHeader 字节数
long biWidth; //位图宽度
long biHeight; //位图高度，正位正向，反之为倒图
unsigned short biPlanes; //为目标设备说明位面数，其值将总是被设为1
unsigned short biBitCount; //说明比特数/象素，为1、4、8、16、24、或32。
unsigned long biCompression; //图象数据压缩的类型没有压缩的类型：BI_RGB
unsigned long biSizeImage; //说明图象的大小，以字节为单位
long biXPelsPerMeter; //说明水平分辨率
long biYPelsPerMeter;//说明垂直分辨率
unsigned long biClrUsed; //说明位图实际使用的彩色表中的颜色索引数
unsigned long biClrImportant;//对图象显示有重要影响的索引数，0都重要。
} __attribute__((packed)) BitMapInfoHeader; //像素点结构体
typedef struct
{
unsigned char Blue; //该颜色的蓝色分量
unsigned char Green; //该颜色的绿色分量
unsigned char Red; //该颜色的红色分量
unsigned char Reserved; //保留值（亮度）
} __attribute__((packed)) RgbQuad; int show_photo(const char *fbp, struct fb_var_screeninfo *scrinfo, const char *bmpname); #endif //__BMP_H__

/************************* *bmp.c文件 *************************/ #include "bmp.h" /************************* *fbp，映射内存起始地址 *scrinfo，屏幕信息结构体 *bmpname，.bmp位图文件名 *************************/
int show_photo(const char *fbp, struct fb_var_screeninfo *scrinfo, const char *bmpname)
{
if(NULL == fbp || NULL == scrinfo || NULL == bmpname)
return -; int line_x = , line_y = ;
unsigned long tmp = ;
int xres = scrinfo->xres_virtual;//屏幕宽（虚拟）
int bits_per_pixel = scrinfo->bits_per_pixel;//屏幕位数
BitMapFileHeader FileHead;
BitMapInfoHeader InfoHead;
RgbQuad rgb; unsigned long location = ; //打开.bmp文件
FILE *fb = fopen(bmpname, "rb");
if (fb == NULL)
{
printf("fopen bmp error\r\n");
return -;
} //读文件信息
if ( != fread( &FileHead, sizeof(BitMapFileHeader),, fb))
{
printf("read BitMapFileHeader error!\n");
fclose(fb);
return -;
}
if (memcmp(FileHead.bfType, "BM", ) != )
{
printf("it's not a BMP file\n");
fclose(fb);
return -;
}

//读位图信息
if ( != fread( (char *)&InfoHead, sizeof(BitMapInfoHeader),, fb))
{
printf("read BitMapInfoHeader error!\n");
fclose(fb);
return -;
}

//跳转至数据区
fseek(fb, FileHead.bfOffBits, SEEK_SET);

int len = InfoHead.biBitCount / ; //原图一个像素占几字节
int bits_len = bits_per_pixel / ; //屏幕一个像素占几字节//循环显示 while(!feof(fb))
{
tmp = ;
rgb.Reserved = 0xFF;

if (len != fread((char *)&rgb, , len, fb))
break;

//计算该像素在映射内存起始地址的偏移量
location = line_x * bits_len + (InfoHead.biHeight - line_y - ) * xres * bits_len;

tmp |= rgb.Reserved << | rgb.Red << | rgb.Green << | rgb.Blue;

*((unsigned long *)(fbp + location)) = tmp;

line_x++;
if (line_x == InfoHead.biWidth )
{
line_x = ;
line_y++;
if(line_y == InfoHead.biHeight)
break;
}
}

fclose(fb); return ;
}

/************************* *main.c文件 *************************/ #include "bmp.h" int main()
{
int devfb, filefb;
struct fb_var_screeninfo scrinfo;
unsigned long screensize;
char *fbp ;
char bmpname[] = {}; //打开设备文件
devfb = open("/dev/fb0", O_RDWR);
if(!devfb)
{
printf("devfb open error!\r\n");
return -;
}
//printf("devfb open OK! %d\r\n", devfb); //获取屏幕信息 //若屏幕显示区域大小不合适，可用ioctl(devfb, FBIOPUT_VSCREENINFO, &scrinfo)设置
if(ioctl(devfb, FBIOGET_VSCREENINFO, &scrinfo))
{
printf("get screen infomation error!\r\n");
return -;
} //printf(".xres=%d, .yres=%d, .bit=%d\r\n",scrinfo.xres, scrinfo.yres, scrinfo.bits_per_pixel); //printf(".xres_virtual=%d, .yres_virtual=%d\r\n",scrinfo.xres_virtual, scrinfo.yres_virtual); if( != scrinfo.bits_per_pixel)
{
printf("screen infomation.bits error!\r\n");
return -;
} //计算需要的映射内存大小
screensize = scrinfo.xres_virtual * scrinfo.yres_virtual * scrinfo.bits_per_pixel / ;
//printf("screensize=%lu!\r\n", screensize);

//内存映射
fbp = (char *)mmap(NULL, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, devfb, );
if(- == (int)fbp)
{
printf("mmap error!\r\n");
return -;
}

scanf("%s", bmpname);

//显示图片
show_photo(fbp, &scrinfo, bmpname); //取消映射，关闭文件
munmap(fbp, screensize);
close(devfb); return ;
}