#pragma pack(1)
 struct _BmpFileHeader
{
    unsigned short    bfType;         //Specifies the file type. It must be BM

    unsigned long     bfSize;     //Specifies the size, in bytes, of the bitmap file

    unsigned long     bfReserved1;     //Reserved; must be zero

    unsigned long     bfRebfOffBits;     //数据区偏移量 Specifies the offset, in bytes, from the BITMAPFILEHEADER structure to the bitmap bits

};

typedef struct _BmpFileHeader BmpFileHeader; //BMP文件头


 struct _BmpInfoHeader
{
    unsigned long biSize;        //Info Header的大小,Specifies the number of bytes required by the structure.

    long biWidth;        //biWidth Specifies the width of the bitmap.单位是像素

    long biHeight;        //Specifies the height of the bitmap, in pixels.

    unsigned short biPlanes;        //Specifies the number of planes for the target device. This value must be set to 1.

    unsigned short biBitCount ;    //BPP值，Specifies the number of bits per pixel,such as 1,4,8,24 .

    unsigned long biCompression;//Specifies the type of compression for a compressed bottom-up bitmap

                        //(top-down DIBs cannot be compressed). This member can be one of the

                        //following values: BI_RGB,BI_RLE8,BI_RLE4,BI_BITFIELDS,BI_JPEG.

                        
    unsigned long biSizeImage;    //图像尺寸,Specifies the size, in bytes, of the image. This may be set to zero for BI_RGB bitmaps.

    
    long biXPelsPerMeter;//Specifies the horizontal resolution, in pixels per meter, of the target device for the

                        //bitmap. An application can use this value to select a bitmap from a resource

                        //group that best matches the characteristics of the current device.

                        
    long biYPelsPerMeter;//Specifies the vertical resolution, in pixels per meter, of the target device for the bitmap.

    
    unsigned long biClrUsed;        //颜色数，Specifies the number of color indexes in the color table that are actually used by the bitmap.

                        //If this value is zero, the bitmap uses the maximum number of colors corresponding

                        //to the value of the biBitCount member for the compression mode specified by biCompression.

                        
    unsigned long biClrImportant;    //Specifies the number of color indexes that are required for displaying the bitmap. If this value is zero,

                        //all colors are required.

};

typedef struct _BmpInfoHeader BmpInfoHeader; //BMP文件信息



  struct _RGBQuad
{
    unsigned char rgbBlue;        //Specifies the intensity of blue in the color.

    unsigned char rgbGreen;    //Specifies the intensity of green in the color.

     unsigned char rgbRed;        //Specifies the intensity of red in the color.

     unsigned char rgbReserved;    //Reserved; must be zero.

};

typedef struct _RGBQuad RGBQuad; //RGB调色板数据


#pragma pack()

BmpFileHeader header;
BmpInfoHeader info;
   
   //读文件头信息

  len = fread(&header,1,sizeof(header),file);
  if(len != sizeof(header))
      {
       printf("bmp file %s header failure\n",file_name);
     fclose(file);
     return -2;
      }
    if(header.bfType!=DIB_HEADER_MARKER)
        {
         printf("bmp file %s no BM \n",file_name);
         fclose(file);
     return -3;
        }
      //读文件信息

     len = fread(&info,1,sizeof(info),file);
    if(len != sizeof(info))
      {
       printf("bmp file %s info failure\n",file_name);
     fclose(file);
     return -4;
      }

#define RGB_24_888(r,g,b) ( ((r & 0xff)<<16) | ((g & 0xff ) << 8) | ((b & 0xff) << 0) )


//注意BMP的RGB数据区是倒排,即图像最后一行存在文件最开始，这样文件中的第一点实际上是左下角数据.

//最后一个点是右上角数据。


int bmp_show_le_24bpp(char * file_name,unsigned char * fb_buf,int buf_len,int width,int height)
{
   FILE * file = NULL;
   int len,i,j,cnt=0;
   unsigned char ary[3]; //BMP的24位是用3byte保存

   unsigned char * p;
   unsigned long value;
   BmpFileHeader header;
   BmpInfoHeader info;

   printf("show BMP file %s,width %d,height %d\n",file_name,width,height);
   
   file = fopen(file_name,"rb");

   
   
   if(file == NULL)
       {
        printf("open bmp file %s failure\n",file_name);
     return -1;
       }

  len = fread(&header,1,sizeof(header),file);
  if(len != sizeof(header))
      {
       printf("bmp file %s header failure\n",file_name);
     fclose(file);
     return -2;
      }

  
    if(header.bfType!=DIB_HEADER_MARKER)
        {
         printf("bmp file %s no BM \n",file_name);
         fclose(file);
     return -3;
        }

     len = fread(&info,1,sizeof(info),file);
    if(len != sizeof(info))
      {
       printf("bmp file %s info failure\n",file_name);
     fclose(file);
     return -4;
      }

   p = (fb_buf+width*(height-1)*4); //移到FrameBuffer最后一行


   printf("bmp %s: fb_buf %x,Height %d,Width %d,bpp %d,data offset %d\n",file_name,fb_buf,info.biHeight,info.biWidth,info.biBitCount,header.bfRebfOffBits);

  //移到数据区

   fseek(file,header.bfRebfOffBits,SEEK_SET);

   //这里假设图像尺寸与屏幕完全一致.

   for(i=0; i< height ; i++)
       {
        //printf("%s:fb buf %x,line[%d]=%x\n",__FUNCTION__,fb_buf,i,p);

        for(j=0;j< width ; j++)
            {
        if(fread(ary,1,sizeof(ary),file)<0)
            break;
         //注意BMP文件中，是按BGR的顺序保存数据

         value = RGB_24_888(ary[2],ary[1],ary[0]);//注意其倒排顺序
           *((unsigned long *)p) = value;
         p+=4;
        
        //if(i<10)

        // printf("point[%d],value %x, red %x,green %x,blue %x\n",i,value,ary[2],ary[1],ary[0]);
            }
     p-= width*4*2; //回退2行,因为内循环移动一行，还要上移一行      
       }
   

   fclose(file);
   
}