我每次都得到BITMAP filesize 0

Question

我正在尝试阅读BITMAPFILEHEADER和BITMAPINFOHEADER。但我每次都得0。我究竟做错了什么。我正在使用c ++。

#include <bits/stdc++.h>

using namespace std;

typedef int LONG;
typedef unsigned short WORD;
typedef unsigned int DWORD;

struct BITMAPFILEHEADER {
  WORD  bfType;
  DWORD bfSize;
  WORD  bfReserved1;
  WORD  bfReserved2;
  DWORD bfOffBits;
};

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

int main(void){
    ifstream file("lena.bmp");

    int begin = file.tellg();
    file.seekg(0, ios::end);
    int end = file.tellg();
    int length = end-begin;

    char* bf = new char[length+1];

    file.read(bf, length+1);
    BITMAPFILEHEADER* file_header = (BITMAPFILEHEADER*)(bf);
    //BITMAPINFOHEADER* info_header = (BITMAPINFOHEADER*)(bf+sizeof(BITMAPFILEHEADER)-1);

    cout << file_header->bfType << endl;
    //cout << info_header->biSize << endl;
    return 0;
}