读取位图中颜色数据，并转换为5:6:5格式

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#pragma pack(2)

/*

        Definitions for Windows 3.0 and above DIB files

*/

typedef unsigned char       BYTE;
typedef unsigned short      WORD;
typedef unsigned long       DWORD;
typedef unsigned short      UINT;
typedef signed long         LONG;

typedef struct tagRGBQUAD
{
    BYTE    rgbBlue;
    BYTE    rgbGreen;
    BYTE    rgbRed;
    BYTE    rgbReserved;
} RGBQUAD;

typedef struct tagRGB
{
    BYTE    rgbBlue;
    BYTE    rgbGreen;
    BYTE    rgbRed;
} RGB;


typedef struct tagBITMAPINFOHEADER
{
    DWORD   biSize;
    LONG    biWidth;
    LONG    biHeight;
    WORD    biPlanes;
    WORD    biBitCount;
    DWORD   biCompression;
    DWORD   biSizeImage;
    LONG    biXPelsPerMeter;
    LONG    biYPelsPerMeter;
    DWORD   biClrUsed;
    DWORD   biClrImportant;
} BITMAPINFOHEADER;

/* constants for the biCompression field */
#define BI_RGB      0L
#define BI_RLE8     1L
#define BI_RLE4     2L

#define   WIDTHBYTES(bits) (((bits)+31)/32*4)
typedef struct tagBITMAPINFO
{
    BITMAPINFOHEADER bmiHeader;
    RGBQUAD          bmiColors[1];
} BITMAPINFO;

typedef struct tagBITMAPFILEHEADER
{
    UINT    bfType;
    DWORD   bfSize;
    UINT    bfReserved1;
    UINT    bfReserved2;
    DWORD   bfOffBits;
} BITMAPFILEHEADER;

int main()
{
    BITMAPFILEHEADER bmphead;
    BITMAPINFOHEADER bmpinfohead;
    RGB rgb;
    WORD pixel;
    char filename[] = "b.bmp";
    FILE *fp,*fp2;
    int off;

    fp = fopen(filename,"rb");
    fp2 = fopen("rs.c","w");

    off = fread((void*)&bmphead,sizeof(BITMAPFILEHEADER),1,fp);
    printf("offset %d,size %d k\n",bmphead.bfOffBits,int(bmphead.bfSize/1024));
    
    fread((void*)&bmpinfohead,sizeof(BITMAPINFOHEADER),1,fp);
    printf("bitcount = %d bisizeimage = %d,width =%d height = %d\n",bmpinfohead.biBitCount,bmpinfohead.biSizeImage    ,
        bmpinfohead.biWidth,bmpinfohead.biHeight);
    
    int height = bmpinfohead.biHeight;
    int width = bmpinfohead.biWidth;
    int l_width =WIDTHBYTES(width* bmpinfohead.biBitCount);//计算位图的实际宽度并确保它为32的倍数


    BYTE  *pClrData=(BYTE *)malloc(height*l_width);   
    memset(pClrData,0,height*l_width);   
    long nData = height*l_width;

    int nRead = fread(pClrData,1,nData,fp);
    printf("%d\n",nRead);
    
    int k;
    int index = 0;
    for(int i=0;i<height;i++){
        for(int j=0;j<width;j++){
            k = i*l_width + j*3;
            rgb.rgbRed = pClrData[k+2];   
            rgb.rgbGreen = pClrData[k+1];   
            rgb.rgbBlue = pClrData[k];   
            pixel = ((rgb.rgbRed)>>3)<<11|(rgb.rgbGreen>>2)<<5|(rgb.rgbBlue>>3);
            index++;
            fprintf(fp2,"0x%x, ",pixel);
            if(index%10==0)
                fprintf(fp2,"\n");
        }  
    }
    printf("%d\n",index);
    fclose(fp2);
    fclose(fp);
    return 0;
}