开发板上显示图片

参考网址：  http://blog.csdn.net/z1179675084/article/details/14645359
                  http://hi.baidu.com/guoggn/item/636e08145b5d39fc746a8461
                  http://blog.chinaunix.net/uid-26669729-id-3077015.html
                  http://blog.csdn.net/luxiaoxun/article/details/7622988

关键：

1）字节对齐问题__attribute__((packed))   最大字节对齐

2） _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  

3） 字节数的统计

#include <stdio.h>#include <stdlib.h>#include <sys/types.h>#include <sys/stat.h>  #include <unistd.h>#include <sys/mman.h> /*map头文件*/#include <linux/fb.h>     #include <fcntl.h> #include <string.h>  #include <arpa/inet.h> //14byte文件头  typedef struct  {       unsigned char  cfType[2];//文件类型，"BM"(0x4D42)       unsigned int  cfSize;//文件大小（字节）       unsigned int cfReserved;//保留，值为0       unsigned int  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  {       unsigned int  ciSize;//BITMAPFILEHEADER所占的字节数       unsigned int ciWidth;//宽度       unsigned int ciHeight;//高度       unsigned short int ciPlanes;//目标设备的位平面数，值为1       unsigned short int  ciBitCount;//每个像素的位数       char ciCompress[4];//压缩说明       unsigned int ciSizeImage;//用字节表示的图像大小，该数据必须是4的倍数       unsigned int ciXPelsPerMeter;//目标设备的水平像素数/米       unsigned int ciYPelsPerMeter;//目标设备的垂直像素数/米       unsigned int ciClrUsed; //位图使用调色板的颜色数       unsigned intciClrImportant; //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;  }__attribute__((packed)) PIXEL;//颜色模式RGB    BITMAPFILEHEADER FileHead;  BITMAPINFOHEADER InfoHead;  static int xres = 0;  static int yres = 0;  static int bits_per_pixel = 0;  static char *fb_addr = NULL;  int show_bmp(char *picname)  {    FILE *fp;      int rc;      int line_x, line_y;      long int location = 0;    char tmp[1024*10];static unsigned short b,g,r;static unsigned short rgb; /*2个字节*/PIXEL pix;   fp = fopen( picname, "rb" );      if (fp == NULL)      {      printf("open errror\n");        return( -1 );      }    printf("Open OK \n");  /* BITMAPFILEHEADER*/   rc = fread( &FileHead, sizeof(BITMAPFILEHEADER),1, fp );      if ( rc != 1)      {          printf("read header error!\n");          fclose( fp );          return( -2 );      }  printf("Read BITMAPFILEHEADER  OK\n");    //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 );      }  /*BITMAPINFOHEADER*/    rc = fread( (char *)&InfoHead, sizeof(BITMAPINFOHEADER),1, fp );      if ( rc != 1)      {          printf("read infoheader error!\n");          fclose( fp );          return( -4 );      }    printf("Read BITMAPINFOHEADER  OK\n");      //跳转的数据区      fseek(fp, FileHead.cfoffBits, SEEK_SET);          //向framebuffer中写BMP图片  rgb高位有效  for  (line_y = 0; line_y<yres; line_y++)    for (line_x = 0; line_x<xres; line_x++)    {           rc = fread(&pix , sizeof(PIXEL),1, fp);  location = line_x*2+(yres-line_y)*xres*2;    r=((pix.red>>3)<<11)&0xfb80;g=((pix.green>>2)<<5)&0x07e0;b=(pix.blue>>3)&0x001f;rgb=r|g|b;*((unsigned short *)(fb_addr+location)) = rgb;   }    fclose( fp );      return  0 ;   }  int main(int argc, char *argv[ ]){      int fbfd,fb_size ;       struct   fb_var_screeninfo  vinfo;   /*记录用户可修改的显示控制参数*/     struct fb_fix_screeninfo finfo;    /*取得缓冲区的物理地址*/// 打开/dev/fb*设备文件      fbfd = open("/dev/fb0",  O_RDWR|O_CREAT, S_IRWXU);       if (fbfd <0 )      {       printf("open error\n");exit(1);      }//需要的 屏幕内存空间的字节数,取得显示屏幕参数if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)){     printf("Error reading variable information.\n");       exit(1);   }        if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo))     {   printf("Error reading variable information.\n"); exit(1);  }    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;  /*可见解析度*/   yres=vinfo.yres;       bits_per_pixel=vinfo.bits_per_pixel;  /* 每像素位数*/ fb_size=xres*yres*bits_per_pixel/8;   /*计算屏幕的总大小（字节)*/ // fd的内存地址空间映射到我们的程序地址空间// void *mmap(void *start, size_t length, int prot, int flags,int fd, off_t offset);  if ( (fb_addr  = (char *)mmap( 0, fb_size, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0) )<0)  {  printf( "mmap error\n" );exit(1);  }     printf("show_bmp\n");   show_bmp( argv[1] );     //删除对象映射     munmap(fb_addr, fb_size);     close(fbfd);    return 0;}

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