//将二十四位位图作灰度化处理
#include<stdio.h>
#include<string.h>
void main()
{
  FILE *fp1,*fp2;
  unsigned char n;
  unsigned buff[55];
  int width,i;
  int height;
  char flag[] = {'\0','\0','\0'};
  fp1 = fopen("e:\\a.bmp","rb");
  fp2 = fopen("e:\\b.bmp","wb");
  fread(flag,1,2,fp1);
  if(strcmp(flag,"BM")!=0)
  {
   printf("文件不存在\n");
   fclose(fp1);
   fclose(fp2);
  }
  fseek(fp1,18,SEEK_SET);
  fread(&width,1,4,fp1);
  fread(&height,1,4,fp1);
  rewind(fp1);
  rewind(fp2);
  fread(buff,1,54,fp1);
  fwrite(buff,1,54,fp2);
  for(i=0;i<height*width;i++)
  {
    fread(buff,1,3,fp1);
    n = (buff[0]+buff[1]+buff[2])/3;
    fwrite(&n,1,1,fp2);
    fwrite(&n,1,1,fp2);
    fwrite(&n,1,1,fp2);
  }
}

i是干嘛的？